Halmstads BK Born in
Gävle,
Sweden, Olsson started his career at
Högaborgs BK. In 2008, he signed a contract with Halmstad, replacing
Martin Fribrock as
left winger as Fribrock departed for
Esbjerg fB in the summer of 2008. Mainly featured as left winger, he also used as a
forward in several games, during
Josep Clotet Ruiz time at Halmstad and the lack of a natural left side defender, Olsson and
Kujtim Bala took turns on playing on the position. As Halmstads BK was relegated from
Allsvenskan in 2011, Marcus announced that he would not sign a new contract with the club and that he would start searching for a new club to play for.
Blackburn Rovers After rejecting a contract from
Djurgårdens IF, and being linked to
Standard Liège and
Viking FK,
Blackburn Rovers confirmed on 31 January that Olsson had signed a two-and-a-half-year contract with the club, joining his twin brother there. Marcus Olsson made his debut for Blackburn Rovers in the 3–0 away defeat to Manchester City in the Premier League on 25 February 2012, playing on the left wing, in front of his twin Martin who played at left back, with both completing a full 90 minutes. He scored his first goal for Blackburn in a 3–3 draw with
Leeds United on 1 September 2012. Olsson was released by Rovers following the conclusion of his contract with the club on 1 July 2014, but after lengthy negotiations signed a new contract for the club on 11 July. He was voted
Blackburn Rovers player of the season for the
2014–15 season.
Derby County On 26 January 2016, Olsson was transferred from Blackburn to
Derby County for an undisclosed fee, signing a three-and-a-half-year contract. Olsson played his full debut on 6 February 2016 against
Fulham, scoring an own goal after 17 minutes. He scored his first goal for the club in a 1–0 win over
Nottingham Forest on 19 March 2016. He was released by Derby County at the end of the 2018–19 season.
Return to Halmstads BK Olsson missed most of the 2020 season and all of 2021 season due to
cruciate ligament injury. Upon recovering, on 28 January 2022 he returned to
Halmstad. ==International career==