Isaksson began his career at localTrelleborgs FF, before spending two years atJuventus. He would later return to Sweden, where he won twoAllsvenskan titles withDjurgården. After two seasons withRennes, he was signed for £2 million byManchester City of thePremier League, where he was not a regular. After four seasons in theEredivisie withPSV, he joinedKasımpaşa in Turkey on a free transfer in 2012. He returned to Djurgårdens IF in 2016 with which he won the2017–18 Svenska Cupen before retiring in 2018.
Born inSmygehamn, Isaksson began his senior career withTrelleborgs FF, where he played two seasons between 1998 and 1999. He became known as a great goalkeeping prospect and was thus bought by Italian clubJuventus in July 1999, but with the likes of Dutch international goalkeeperEdwin van der Sar in the squad, Isaksson never played a competitive first-team game for theTurin-based club.
After the2006 FIFA World Cup, Isaksson completed a £2 million move toManchester City of thePremier League on 15 August 2006. He was expected to replaceDavid James as their first choice goalkeeper, but due to knee and ankle injuries[6] and the form ofNicky Weaver, he did not achieve this. He made his debut on 9 December 2006, when he replaced the injured Weaver at half-time in aManchester derby match which City lost 3–1 toManchester United.[7] After his second start for City on 14 March 2007, he played all of the remaining ten games of2006–07, keeping fourclean sheets, and saved apenalty kick fromJermain Defoe on the last day of the season, although City nonetheless lost 2–1 toTottenham Hotspur.[8]
Isaksson played the majority of City's next pre-season campaign in Sweden and Belgium, but after his thumb was fractured in a training session, he did not play for City in the first two months of2007–08, picking up a knee injury right afterwards. Isaksson made his first appearance of the season for Manchester City by keeping a clean sheet in a 1–0 away win againstBolton Wanderers to put the team into the quarter-finals of theLeague Cup, on 31 October 2007.[9] In November and December. he had a run of five league games in the first team, as part of a rotation used by managerSven-Göran Eriksson to decide upon his first-choice goalkeeper. His run, however, was ended by an injury. While he was out,England under-21 goalkeeperJoe Hart took over in goal and impressed. The youngster kept his place even after Isaksson returned to full fitness and the Swede was once again relegated to the bench.
Manchester City confirmed that they would be willing to sell Isaksson at the end of the season, and his final appearance was in the humiliating 8–1 defeat byMiddlesbrough, which would have been even worse if not for several excellent saves by Isaksson.[10]
Isaksson signed for Dutch championsPSV, thus enabling him to play in theUEFA Champions League.[11] He took over the number 1 shirt fromHeurelho Gomes, who had transferred to Tottenham. Isaksson tallied 124 league appearances for PSV before leaving the club in the summer of 2012 when his contract expired.
On 9 July 2012, it was confirmed that Isaksson had left PSV after four seasons to join newly promoted Turkish sideKasımpaşa on a free transfer.[12] On joining the club, Isaksson signed a three-year deal and became the Turkish side's sixth signing during the summer transfer window.[13]
On 11 August 2016, Isaksson signed a two-and-a-half-year contract withDjurgården, returning after 12 years away from Sweden and the club.[14] On 24 August, he played his first game in his second spell for Djurgårdens in the Swedish Cup qualifier, a 5–1 win againstSmedby. He conceded one goal in the final minute from a penalty.[15] On 7 August 2017, Isaksson made his 100th match in Allsvenskan for Djurgårdens. On 10 May 2018, he played as they beatMalmö 3–0 in theSwedish Cup Final.[16]
While at Djurgården, Isaksson established himself as the second-choice goalkeeper afterMagnus Hedman for theSweden national team, making his international debut againstSwitzerland in March 2002.[17] An injury to Hedman allowed Isaksson the opportunity to play for Sweden on a regular basis, playing in all but one of Sweden's qualifying matches forUEFA Euro 2004, and all of Sweden's matches during the tournament.
Isaksson remained the first-choice goalkeeper for his national team since Euro 2004, making three appearances in the2006 FIFA World Cup in Germany. An injury prevented him from playing in more games. By July 2006, he had amassed 42 caps for his country.
Isaksson was selected for Sweden'sEuro 2008 squad, and appeared in all three of Sweden's group games. He kept a clean sheet in Sweden's first match againstGreece, which ended 2–0,[18] but Sweden were unable to reach the quarter-finals.
Isaksson was also the first-choice goalkeeper through Sweden's disappointing qualification campaign for the2010 World Cup in South Africa as well as the qualifying rounds forEuro 2012 in Poland and Ukraine. On 29 May 2012, national team managerErik Hamrén announced his final 23-man squad for the Euros, including the vastly experienced Isaksson.[19] Isaksson again appeared in all three group games as Sweden failed to make it out of the group, although he did keep a clean sheet in their 2–0 victory overFrance in the final match.[20]
After Sweden's disappointingEuro 2016 performance, in which Sweden once again failed to progress from the group, Isaksson announced his intention to retire from international football.[22] He amassed 133 caps for his country, effectively making him their third most capped player.