Midtjylland Born in
Horsens, Kjær started playing football when he was four years old. He was one of the first players to graduate from FCM's football academy, the first of its kind in Denmark, coming through the system alongside Midtjylland teammates Jesper Weinkouff,
Christian Sivebæk and former teammate,
Winston Reid. Kjær started out playing in the midfield position before one of his coaches switched him to a defender position, a position he played until retirement. While at the club system, Kjær was named the best player of a French youth tournament in April 2006. This resulted in Midtjylland subsequently rejecting offers from
Lille OSC for Kjær and
Jesper Juelsgård. Kjær made his senior debut for Midtjylland in the
Viasat Cup training matches in June 2006, Two months later, he signed his first professional contract, keeping him until 2009. Kjær was promoted to the first team squad in January 2007. He had a successful trial with
Real Madrid in August 2007, but their transfer offer was refused by FC Midtjylland. Soon after, Kjær signed a five-year contract with Midtjylland instead in September 2007. Kjær made his Superliga debut on 30 September 2007, in the 2–0 victory against
AGF By October 2007, his performances attracted the likes of
Premier League clubs
Middlesbrough and
Chelsea. He went on to play three more matches in the first half of the
Danish Superliga 2007–08 season. Kjær played all 15 games in the second half of the Superliga season, forming a defensive partnership with
Magnus Troest. He kept three consecutive clean sheets between 29 March 2008 and 13 April 2008 against
OB,
Copenhagen and
AaB.
Palermo In February 2008, Kjær signed a five-year contract with Italian club
Palermo, effective from the summer 2008, earning Midtjylland a €4 million
transfer fee. On 5 June 2008, he was presented at the club's press conference alongside new signing,
Andrea Raggi. However, his start to his Palermo's career suffered a setback when Kjær faced competitions in the club's defence, as well as, adapting in Italy. On 26 October 2008, he made his Palermo debut, coming on as a half-time substitute against
Fiorentina in Serie A, as they lost 3–1. After the match, his performance was praised by the club. This was followed by making his first start for the club, as they drew 1–1 against
Lecce three days later. Kjær scored his first goal for Palermo in his third appearance on 2 November 2008, as well as, setting up the club's first goal of the game, in a 3–0 win over
Chievo. He has been involved in the first team, establishing himself in the starting eleven, playing in the centre-back position. Due to his physical strength and tenacity, Kjær's performance continued to improve and was named the second best player under 21 in Serie A by
La Gazzetta dello Sport. It wasn't until 15 March 2009 when he scored his second goal of the season, in a 5–2 win against Lecce. Kjær then scored his third goal of the season, in a 4–1 win against
Bologna on 19 April 2009. For his performance, he was named Serie A's Team of the Week. Kjær ended the
2008–09 season as the club's top scoring defender in Serie A with three goals in 27 appearances in all competitions. in 2009 Kjær confirmed his reputation as a first team regular in the
2009–10 season, and formed a strong defensive partnership with fellow centre-back
Cesare Bovo. As a result, he signed an improved contract with the Sicilian club in September 2009. From the start of the 2009–10 season, Kjær started in every match until he missed one match, due to suspension. He returned to the starting line-up from suspension, playing the whole game, as Palermo lost 5–3 against
Inter Milan on 29 October 2009. A week later on 8 November 2009, Kjær scored his first goal of the season, in a 3–1 loss against Bologna. He was named 2009 Danish Talent of the Year in November 2009, beating
Arsenal's
Nicklas Bendtner and
Ajax's
Christian Eriksen after his successful first season in Palermo. In January 2010, he was also named as
Danish Footballer of the Year for 2009. The next day, Kjær celebrated with a goal against
Cagliari that decided the match for Palermo as the match ended 2–1. Since returning from suspension, he started in the next ten league matches before being suspended once again. After serving a one match suspension, Kjær returned to the starting line-up against Fiorentina on 24 January 2010 and helped the club keep a clean sheet, in a 3–0 win. He started in the next nine league matches before being sent–off for a second bookable offence, in a 2–2 draw against
Genoa on 24 March 2010. After serving a one match suspension, Kjær returned to the starting line–up against
Catania on 3 April 2010, as they lost 2–0. He later started the remaining matches of the 2009–10 season and helped the side finish fifth place to qualify for the
UEFA Europa League. At the end of the 2009–10 season, Kjær scored twice in a total 35 Serie A games (which was 38 appearances and scoring two times in all competitions).
VfL Wolfsburg On 30 June 2010,
VfL Wolfsburg confirmed they had opened talks with Kjær. It came after reported interest from teams across Europe, including English sides
Manchester United,
Manchester City and
Tottenham Hotspur plus Italian side
Juventus. The move was confirmed on 8 July 2010, as the club signed Kjær for an undisclosed fee believed to be in excess of £10 million. Following his move to Wolfsburg, Kjær said:
"The transfer means I have the chance to play for a top club, I think this is the right step for me. We have a strong team that can challenge at the top of the Bundesliga. First, I need to secure a regular place." The deal made Kjær the most expensive Danish footballer of all time. Making the shift from Serie A football to the Bundesliga meant that Kjær would become one of the best paid Danish footballers with an annual salary of around €3 million. Both national coach
Morten Olsen and the player, himself, agreed that the move to Wolfsburg was not only economically justifiable for the young Danish defender but also the shift that this was a step in the right direction for his development. Kjær made his unofficial debut for VfL Wolfsburg in a pre-season fixture against
FC Augsburg, in which Wolfsburg ran out 1–0 winners. His VfL Wolfsburg debut came on 15 August 2010, starting the whole game, in a 2–1 win against
Preußen Münster in the first round of the
DFB-Pokal. He made his
Bundesliga debut for Wolfsburg in a 2–1 loss against
Bayern Munich five days later on 20 August 2010. After a poor start to the season for Wolfsburg, with varying results and unmet expectations; Kjær scored his first goal for Wolfsburg in a 2–0 win over
Stuttgart when he headed the ball in over the line after a corner kick. However, the goal was eventually credited to
Edin Džeko after it was shown that the ball took a deflection from Džeko's shot. Despite much criticism from the media for his poor performances, Kjær played in the starting line-up in all 17 Bundesliga matches in the autumn 2010 season. After having formed a successful partnership with
Italy international
Andrea Barzagli in Wolfsburg's central defence, he then featured alongside
German international
Arne Friedrich. On 22 January 2011, Kjær scored his first Bundesliga goal with a headed goal in the 83rd minute, in a 1–0 win against
Mainz 05, a win that secured the first club victory in eight matches – after seven drawn games in a row. Following
Steve McClaren's sacking (who brought him to the club) due to further poor results in February 2011,
Felix Magath returned to Wolfsburg (the manager guided the club to win their first Bundesliga title) and commented on criticising the 'poor condition' of the players he inherited (including Kjær) from McClaren. In connection with the dismissal, Kjær declared affection for Steve McClaren in public. Kjær said he was sorry for the firing, and was happy to work with Steve McClaren. Despite the comment from Magath, Kjær continued to regain his first team place for the rest of the 2010–11 season, though it was met by frustration, as the club narrowly avoided the drop the previous season and he had come under fire for some lacklustre displays. Despite being on the sidelines on three occasions during the 2010–11 season, he made 34 appearances and scoring once in all competitions. In the summer transfer window 2011, Kjær revealed that head coach Magath told him that he would be allowed to leave that summer and reported that he had fallen out of favor with Magath. Amid the transfer speculation, Kjær made four appearances for Wolfsburg before departing for Roma.
Loan to Roma Italian side
Roma revealed the club were on the verge of signing Kjær on a €10 million move from Wolfsburg as a replacement for centre-back
Philippe Mexès who left for AC Milan on a free transfer. However, the move to Roma was put back on hold after reports in Italy claimed the defender had been recalled by his club Wolfsburg. Instead on 30 August 2011, Kjær went out on a season-long loan deal to Roma, with the option to purchase at the end of the season. Kjær made his debut for Roma in a 0–0 draw against Inter Milan on 17 September 2011. However, in a 2–1 loss against
rivals,
Lazio on 16 October 2011, he received a straight red card in the 50th minute for a foul on
Cristian Brocchi, resulting in a penalty and was successfully converted by the opposition team. After the match, Kjær missed the next four matches, due to suspension and his own injury concern. On 20 November 2011, he returned to the starting line-up against Leece, as the club won 2–1. However, his return was short-lived when Kjær suffered an injury that kept him out for a month. On 11 January 2012, he returned to the starting line–up for Roma's match against Fiorentina in the Round of 16 of the Coppa Italia and helped the side keep a clean sheet, in a 3–0 win. However, during the club's 4–2 defeat to
Cagliari on 1 February 2012, Kjær was at fault for his poor performance and was largely disappointing for Roma. After the match, Roma director
Walter Sabatini dropped a strong hint that the club may decide against signing Kjær on a permanent basis due to his poor performance at Roma. He continued to remain in the first team for the rest of the 2011–12 season. Despite being sidelined on two more occasions later in the 2011–12 season, Kjær made 24 appearances in all competitions. Following this, Roma decided against signing Kjær permanently, citing his poor performances.
Return to Wolfsburg After his loan-spell at Roma ended, Kjær stated he would not return to Wolfsburg, after coach Magath decided the Dane was not going to be part of his first team plans for the club's
2012–13 season. However, Magath changed his mind by announcing that he was willing to bury the hatchet with Kjær, and keen to bring him into his first team at Wolfsburg. He made his first appearance for Wolfsburg in the opening game of the 2012–13 season against
VfB Stuttgart, coming on as a late substitute, in a 1–0 win. After missing the follow-up match against
Hannover 96 due to a potential transfer to
Galatasaray, which later collapsed, Kjær returned to the starting line-up against
FC Augsburg on 16 September 2012, as they drew 0–0. After the match, both he and his Danish compatriot
Thomas Kahlenberg were praised by Manager Magath. However, Kjær found himself placed on the substitute bench in the first three months to the season. Following Magath's sacking, he returned to the starting line-up against
Fortuna Düsseldorf on 27 October 2012, as the club won 4–1. Soon after, Kjær regained his first team place, playing in the centre-back position under the new management of
Lorenz-Günther Köstner and
Dieter Hecking. On 2 December 2012, he scored his first goal of the season, in a 1–1 draw against
Hamburger SV. A month later on 19 January 2013, Kjær set up the club's second goal of the game, in a 2–0 win against Stuttgart. Following the criticism of his performance against Hannover 96 on 26 January 2013, he was dropped to the substitute bench for the next three matches. But Kjær made his return to the starting line–up against Mainz 05 on 23 February 2013, in a 1–1 draw. Following the match, he regained his first team place for the next seven matches. Kjær then scored his second goal of the season, in a 1–1 draw against
Bayer Leverkusen on 6 April 2013. Two weeks later on 20 April 2013 against
Werder Bremen, he set up Wolfsburg's first goal of the game before being substituted in the 54th minute after suffering an abductor problem. Following the match, Kjær never played for the club for the rest of the 2012–13 season. At the end of the 2012–13 season, he went on to make 25 appearances and scored two times in all competitions.
Lille LOSC in 2014 On 5 July 2013, it was announced that Kjær had signed a four-year deal with
Ligue 1 side,
Lille. About the club, he said: "I think this is the right time for me to come to LOSC. Whether it is in my progression, from a geographical point of view, or in relation to the people who live in this region, it is obvious that the idea of joining such a club can only be the good one." Kjær made his Lille debut in the opening game of the season against
FC Lorient, where he kept a clean sheet, in a 1–0 win. Since making his debut for the club, he quickly established himself in the starting eleven, playing in the centre-back position, forming a partnership with
Marko Baša. Kjær helped Lille keep two consecutive clean sheets between 25 August 2013 and 31 August 2013 against
Saint-Étienne and
Rennes. Once again, he helped the club keep ten consecutive clean sheets between 24 September 2013 and 3 December 2013. Kjær then set up Lille's only goal of the game, as they lost 2–1 against
Stade de Reims on 12 January 2014. Nine days later on 21 January 2014, he scored his first goal for the club, in a 3–0 win against
Iris Club de Croix in the second round of the Coupe de France. Kjær impressed during his first season in the French Ligue 1 as leader of the best defence in the major European national leagues in the 2013–14 season conceding only 26 goals in 38 matches including an impressive number of 21 clean sheets. As a result of the solid performances Kjær frequently appeared on various media's team of the week during the entire season, eventually earning a spot on "the Ligue 1 Team of the Season" alongside teammate and goalkeeper
Vincent Enyeama. Despite missing three matches during the 2013–14 season, he made 37 appearances and scoring once in all competitions. At the start of the 2014–15 season, Kjær played in both legs in the third round of the UEFA Champions League qualifying round against
Grasshopper, as he helped Lille win 3–1 on aggregate to advance to the next round. Kjær then kept three consecutive clean sheets in the first three league matches, including scoring his first ever
Ligue 1 goal against
Lorient with a deflected free kick. He continued to regain his first team place, playing in the centre-back position. Kjær then scored on his UEFA Europa League debut, in a 1–1 draw against
FC Krasnodar on 18 September 2014. Once again, he kept three consecutive clean sheets between 7 January 2015 and 14 January 2015, including scoring his second goal of the season, in a 2–0 win against
FC Nantes in the quarter–finals of the Coupe de la Ligue. However, Kjær suffered a thigh injury during a match against Lorient on 17 January 2015 and was substituted in the 33rd minute, resulting in him missing two matches. He returned to the starting line-up against
Montpellier on 7 February 2015, as the club won 2–1. Since returning to the first team from injury, Kjær continued to regain his first team place, playing in the centre-back position. Despite being sidelined on five occasions during the 2014–15 season, he went on to make 42 appearances and scored three times in all competitions.
Fenerbahçe in a
UEFA Champions League match against
Shakhtar Donetsk in 2015 Following a transfer speculation over the summer, it was announced on 16 June 2015 that Kjær joined Turkish side
Fenerbahçe, signing a four-year deal for €7.65 million. Kjær made his Fenerbahçe debut, starting the whole game, in a 0–0 draw against
Shakhtar Donetsk in the first leg of the UEFA Champions League third round. However, in a return leg, he was sent–off for the second bookable offence, as the club lost 3–0, eliminating them from the tournament. Kjær then made his league debut for Fenerbahçe, starting the whole game, as they drew 1–1 against
Çaykur Rizespor. However while on international duty, he suffered an ankle injury that saw him out for three weeks. On 27 September 2015, Kjær returned to the starting line–up against
Beşiktaş, only for him to score an own goal, as the club lost 3–2. As a result, his performance was subjected of criticism, due to picking up cards in his first seven official matches. Despite this, he continued to regain first team place, playing in the centre–back position. Over time, his performance began to improve. On 28 December 2015, Kjær scored his first goal for Fenerbahçe, in a 2–1 win against
Sivasspor. He then helped the club keep five consecutive clean sheets between 20 February 2016 and 3 April 2016. Kjær, once again, helped Fenerbahçe keep four consecutive clean sheets between 20 April 2016 and 5 May 2016, including helping the side reach the
final of the Turkish Cup by beating
Konyaspor 5–0 on aggregate and scoring his second goal of the season, in a 3–0 win against
Gaziantepspor. He then started in the final against
rivals,
Galatasaray, as they lost 1–0. Despite being sidelined on three more occasions later in the 2015–16 season, Kjær made 45 appearances and scoring two times in all competitions. in 2016 At the start of the 2016–17 season, Kjær captained in both legs of the UEFA Champions League third round qualifying round against
AS Monaco, losing 4–3 on aggregate. In a match against
Kayserispor on 28 August 2016, he scored Fenerbahçe's first goal of the game but was sent off for a straight red card nine minutes later, as the club drew 3–3. After serving a one match suspension, Kjær scored on his return in the UEFA Europa League match against
Zorya Luhansk on 15 September 2016. Since returning from suspension, he continued to regain his first team place, playing in the centre-back position. Two months later on 24 November 2016, Kjær scored against Zorya Luhansk in the UEFA Europa League match, as the club won 2–0. He then helped the club keep two consecutive clean sheets on two separate occasions throughout December. However, later in the 2016–17 season, Kjær was plagued with injuries on five occasions. Despite this, he continued to be involved in the first team for Fenerbahçe. In his second season at the club, Kjær went on to make 43 appearances and scoring three times in all competitions.
Sevilla As a result of Fenerbahçe's ban from playing European football next season, this led Kjær wanting to leave the club as a result. On 2 August 2017, Kjær joined Spanish side
Sevilla, signing a four-year deal for a transfer fee of €12,500,000. in 2017|left Kjær made his Sevilla debut in the opening game of the season, starting the whole game, in a 1–1 draw against
RCD Espanyol. By September, he was sidelined with injuries on two occasions. Kjær then scored his first goal for the club, in a 5–1 loss against
Spartak Moscow on 17 October 2017. He became a first team regular for the next two months, playing in the centre–back position. This lasted until Kjær injured his left abductor muscle while training and missed three matches as a result. On 6 December 2017, he returned to the starting line-up against
Maribor and helped the club draw 1–1. In
the first leg of the Copa Del Rey Round of 16, Kjær set up the club's second goal of the game, in a 2–1 win. Three days later on 6 January 2018, he scored his first league goal for Sevilla, in a 5–3 loss against
rivals,
Real Betis. However, Kjær suffered a back injury that kept him out for a month. On 28 February 2018, he returned to the starting line-up against
Málaga and helped the club keep a clean sheet, in a 1–0 win. Kjær started in the next five matches for Sevilla since returning from injury and proved to be instrumental as he helped the club beat
Manchester United in the second leg of the UEFA Champions League Round of 16. However, during a 4–0 loss against
Celta Vigo on 7 April 2018, Kjær suffered a knee injury and was substituted in the 40th minute. On 12 May 2018, he returned to the starting line–up against rivals, Real Betis, and scored his second league goal of the season, in a 2–2 draw, a result that guaranteed Sevilla's qualification of playing European football next season. At the end of the 2017–18 season, Kjær made 27 appearances and scoring three times in all competitions. Following this, he reflected on his first season at the club, saying: "Personally, it has been a strange year ... Next year I will continue to improve. Not having injuries would be a great help." At the start of the 2018–19 season, Kjær started the whole game in the
Supercopa de España against
Barcelona, as Sevilla lost 2–1. He regained his first team place, playing in the centre-back position, for the club. This lasted until a match against
SD Huesca on 28 October 2018 when Kjær suffered a hamstring injury in the 24th minute and was substituted as Sevilla won 2–1. Following this, it was announced that he would be sidelined for a month. On 25 November 2018, Kjær returned to the starting line-up against
Real Valladolid and kept a clean sheet, in a 1–0 win. He continued to found in and out of the starting line-up despite being plagued by injuries as the 2018–19 season progressed. Despite this, Kjær made 37 appearances in all competitions. Following this, it was expected that he'll be leaving Sevilla ahead of the 2019–20 season.
Loan to Atalanta On 1 September 2019, Kjær was loaned to
Atalanta. Kjær made his Atalanta debut, starting the whole game, in a 2–0 win against Roma on 24 September 2019. He then appeared four more times throughout October. However, just like
Martin Škrtel (his former teammate at
Fenerbahçe who signed and terminated his contract with Atalanta within August 2019), he failed to convince the team's head coach
Gian Piero Gasperini. As a result, the club chose to terminate the loan deal six months ahead of expiration.
AC Milan On 13 January 2020, Kjær signed with
AC Milan on loan for the rest of the 2019–20 season, with the option to make the transfer permanent for an undisclosed sum. He had been linked with the club in the late 2000s and early 2010s during his time with
Palermo and even praised in the media by then-current Milan's head coach
Carlo Ancelotti yet the move eventually broke down as two clubs failed to agree on his transfer fee. Desiring to pick up a squad number that would have number 4 in it, Kjær chose 24 that once belonged to fellow Danish international defender
Martin Laursen who played for Milan from 2001 to 2004. He also became the first Dane to play for the club since 2005, when
Jon Dahl Tomasson transferred out. On 15 January 2020, Kjær made his debut for the club, playing for 82 minutes in a home 3–0 win against
S.P.A.L. in the round of 16 of the
Coppa Italia. Four days later, he played his first game in
Serie A as a Milan player in a dramatic 3–2 home win against
Udinese. After missing one match due to illness, Kjær returned to the starting line-up, playing in the centre–back position, losing 4–2 against
rivals, Inter Milan on 9 February 2020. However, his return was short–lived when he torn his muscle injury and was substituted in the 44th minute, in a 1–0 win against
Torino on 17 February 2020. After the match, it was announced that Kjær would be out of action for a few months. Due to the
COVID-19 pandemic which resulted in the suspension of League matches, he managed to recover from his injury and returned to the starting line-up in the second leg of the Coppa Italia semi-finals against Juventus; the club drew 0–0, resulting in Milan's elimination from the tournament. In his debut season under head coach
Stefano Pioli, Kjær would compete with other central defenders, namely
Mateo Musacchio,
Léo Duarte, and
Matteo Gabbia, for a starting line-up spot in the team's back four alongside left central defender and captain
Alessio Romagnoli. He would make 11 more appearances for Milan (9 in Serie A and 4 in Coppa Italia) before the club bought him out from Sevilla for €3.5 million on 15 July 2020, the expiry date of the buy-out clause in his loan deal. On 15 July 2020, Kjær signed a permanent deal with Milan until 30 June 2022. On 11 March 2021, Kjær scored his first goal for the Rossoneri in a 1–1 away draw against
Manchester United in the first leg of the
Europa League round of 16 tie. On 27 October 2021, Kjær extended his contract with Milan until 2024. On 1 December 2021, in the opening minutes of the Serie A away game against
Genoa, Kjær sustained an injury to his left knee and had to be stretchered off the pitch. After surgery on the anterior cruciate ligament, he was ruled out for six months. On 22 May 2022, as Milan won 3–1 against
Sassuolo at the
Stadio Città del Tricolore, Kjær became the Serie A champion with the rest of the team, helping the club win its first major silverware in 11 years as well as winning the first major trophy in his own entire career. On 21 May 2024, AC Milan announced that Kjær would leave the club after his contract expired ahead of the last game of the season, a home game against
Salernitana. On 13January 2025, after spending six months as a
free agent, Kjær officially announced his retirement from professional football at 35years old. ==International career==