Early career Giakoumakis was born and grew up in
Heraklion, Crete, where he started his career in local teams. He began his professional career
Atsalenios in his hometown, Heraklion. In 2012, he signed for
Platanias, in
Chania and he debuted for the club in a 3–2 win against
Skoda Xanthi, coming in as a substitute in the 78th minute. In January 2014 he signed for
Episkopi in
Rethymno on loan until the end of the season and he made a total of 11 appearances and scoring two goals. He returned to Platanias, starting playing more often in the
2014–15 season and on 26 April 2015, he scored his first
Super League goal, in a 2–0 home win
Panetolikos.
AEK Athens On 26 June 2017, Giakoumakis left Crete to join one of Athens' major clubs,
AEK Athens on a four-year contract. On 20 December, he scored his first goal with the club in a 4–0 away
Greek Cup win against
Panetolikos. On 4 February, he scored as a late substitute in stoppage time in 2–1 away win game against champions
Olympiacos. It was his first goal in
Super League with AEK. He scored his first goal for the
2018–19 season, in a 2–1 home win against
Lamia for the
Greek Cup, taking advantage of
Lucas Boyé's excellent solo effort.
Loans to OFI and Górnik Zabrze On 24 January 2019, after a year-and-a-half with
AEK Athens, Giakoumakis returned briefly to his hometown in Crete to join the island's biggest team,
OFI. He signed a six-month contract as part of the club's effort to avoid relegation, with an undisclosed purchase option for the summer of 2019. On 17 March 2019, he scored his first goal with the club in a crucial 2–0 home win over fellow strugglers
Levadiakos to climb above their Super League rivals, however both clubs still sit in the relegation zone. On 3 March 2020, he was loaned out to
Ekstraklasa club
Górnik Zabrze for the remainder of the current football season. On 30 May 2020, Giakoumakis scored the winning goal for Górnik Zabrze against
ŁKS Łódź sealing a vital 1–0 away win for his club. On 23 June 2020, Giakoumakis scored his third goal for Górnik Zabrze in the Ekstraklasa, while teammate
Stavros Vasilantonopoulos registered his second marker for the club in the same match. The Greek striker connected with a low pass across the box, neatly turning the ball beyond the goalkeeper into the far right corner, sealing a 3–1 away win against
ŁKS Łódź.
VVV-Venlo On 11 August 2020, Giakoumakis moved to
VVV-Venlo. He signed a two-year contract with an option for an additional year with the Dutch club, while AEK Athens received a transfer fee of €600,000. On 12 September, in his first game for VVV, Giakoumakis led his new club to win against
FC Emmen by scoring a hat trick in the
2020–21 Eredivisie opener. The Greek forward scored all his goals in the second half, overturning the score, as the hosts were leading up to that point with 2–0. On 14 January 2021, Giakoumakis scored all four goals in a 4–1 away victory at
ADO Den Haag. Two weeks later, on 28 January 2021, he again scored all four goals in a 4–1 victory: this time at home to
Vitesse, and joined former
Ajax striker
Luis Suárez as the only players in the 21st century to have twice scored four goals in a single
Eredivisie game. He was voted Eredivisie Player of the Month for January, having scored the most goals in Netherlands in a calendar month since 1985, and the second-most to
Marco Van Basten's 12 with
Ajax. On 14 March, VVV-Venlo may have suffered its seventh consecutive defeat in the
Eredivisie, however Giakoumakis with the goal he scored against
Fortuna Sittard in an 3–1 home loss, made history as he caught Hans Sleven, who in the
1958–59 season had scored 24 goals in one year, rising to the fifth place of the scorers of all times for the club. On 13 May, Giakoumakis scored in VVV-Venlo's defeat in a crucial match against champions
Ajax. After a reasonably good start to the competition, the club was unable to win the last fourteen matches in the league and was relegated while Giakoumakis became top scorer of Eredivisie.
Celtic During the summer window, Giakoumakis was wanted by various clubs, with German club
Werder Bremen agreeing a transfer fee with Venlo. On 31 August 2021, the last day of the summer
transfer window, he signed for
Scottish Premiership club
Celtic on a five-year contract for a fee of £2.5 million. A month later, he made his debut as a substitute in a 4–0 home loss against
Bayer Leverkusen in the
UEFA Europa League. On 23 October, Giakoumakis scored his first goal for Celtic, opening the scoring in a 2–0 league win against
St Johnstone. On 22 January 2022, Giakoumakis started for the first time in three months and rewarded
Ange Postecoglou with a goal in a 2–1 away win over
Alloa Athletic in the fourth round of the
Scottish Cup. On 26 January, he scored in a vital 2–1 away win against
Heart of Midlothian. On 20 February, Giakoumakis scored a hat-trick in a 3–2 win against
Dundee. On 14 March, Giakoumakis scored twice to help beat
Dundee United and book their place in the semi-finals of the
Scottish Cup. On 19 March, he scored his second hat-trick in five games as Celtic beat in-form
Ross County 4–0 to move six points clear of Rangers at the top of the table. His efforts in March earned him the
SPFL Player of The Month award. On 11 May, Giakoumakis scored in a 1–1 draw at
Dundee United which secured the
2021–22 Scottish Premiership title for Celtic. On the final day of the season, Giakoumakis scored a double after coming off the bench against
Motherwell to become the joint top goalscorer in the league. This was despite playing in only 21 games, which was 16 fewer than
Regan Charles-Cook who also scored 13. His performances that season led to him becoming a popular player amongst the Celtic support, who made a chant in his honour based on German band
Nena's single
99 Luftballons. On 8 October, Giakoumakis scored a dramatic 95th-minute winner in a 2–1 victory at
St Johnstone; only a few minutes after the home side had equalised via
Alex Mitchell. He would go on to make appearances in the
UEFA Champions League for Celtic, starting in their opening group stage match against
Real Madrid. He scored in a 1–1 draw at home against
Shakhtar Donetsk on 25 October. In December, media reports emerged claiming that Giakoumakis was unhappy with terms offered to him by Celtic in contract negotiations. He was linked with a move to Saudi Arabia. Giakoumakis later became linked to both
Atlanta United and
Urawa Red Diamonds in January, with multiple reports indicating Atlanta offering a transfer fee of £4.3 million. Celtic confirmed his transfer on 8 February 2023.
Atlanta United On 5 March 2023, Giakoumakis made his MLS debut, playing in Atlanta's 1–1 draw with
Toronto FC. On 8 November 2023, in Atlanta's 4–2 win over
Columbus Crew, the Greek striker became the first player in club history to contribute to three goals in a single MLS Cup Playoffs match. On 28 November 2023, Giakoumakis was included in the selection of the Best XI presented by
Continental Tire, which recognizes the league’s top players at each position as determined by members of the media, MLS players and MLS club technical staffs. On 9 March 2024, Giakoumakis scored his first hat-trick for the club in a 4–1 win over
New England Revolution. He tallied 24 goals and seven assists in 43 matches across all competitions for Atlanta.
Cruz Azul On 16 June 2024, Giakoumakis joined Mexican club
Cruz Azul. The Greek international departs for a reported $10 million, opening a Designated Player spot as Atlanta enter the summer transfer window. He initially joined in February 2023 from Scotland's Celtic FC, earning
2023 MLS All-Star Game, Best XI and
MLS Newcomer of the Year Award honors last year while helping replace club legend
Josef Martínez. ==International career==