Born in Thun, Switzerland to a family of Bosnian Serb expats (his father hails from the Skugrić village near Modriča), Kuzmanović continued the family tradition as both his father Ljubo and his grandfather played football for the lower league in Bosnia and Herzegovina at the local club in Gradačac – FK Zvijezda where he started his football career.

[2] Kuzmanović's father also played professionally in Berlin, before eventually ending his career at FC Thun of Switzerland, and continuing to live in the country.

On 30 January 2007, at the age of 19, he signed a four-and-a-half-year contract with ACF Fiorentina after learning its midfielder Marco Donadel would be away for about two months because of a calf injury.

In his first full season at Fiorentina, Kuzmanović managed to established himself in the first team and then scored his first goal for the club against Catania on 17 February 2008.

[10] In the UEFA Cup campaign knockout stage in the quarter-final against Everton, Kuzmanović scored his first European goal in a 2–0 win in the first leg.

[11] In the second leg, Everton managed to catch up with a 2–0 win, resulting an extra time and the game played on the penalties, which Fiorentina won 4–2.

During his time at the club, Kuzmanović went on to become an integral first team player for Fiorentina, notching up over 70 Serie A appearances and featuring in their successful European competition runs.

[19] Kuzmanović established himself in the starting eleven, taking the first team place from Thomas Hitzlsperger[20] and made thirty–four appearances and scoring five times in all competitions despite injury.

[21] Kuzmanović managed to regain his first team place and started the 2010–11 season well when he scored his first goal of the season, in a 7–0 thrash victory over Borussia Mönchengladbach on 18 September 2010,[22] Kuzmanović’s performance soon attracted interests from Serie A clubs, but he played down rumours of leaving Stuttgart, insisting he was happy to stay at Stuttgart.

In the 2011–12 season, transfer speculation to sign Kuzmanović continued when English side Chelsea had their 23 million bid turned down.

[35] Kuzmanović played a role in both legs of the Europa League Qualification Round when he provided two assists in both games against Stjarnan.

[38][39] It was not until 29 October 2014 when he made his first league appearance of the 2014–15 season and provided the assist in the only goal of the game, in a 1–0 win over Sampdoria.

Ahead of the 2015–16 season, Kuzmanović's future at Inter Milan became uncertain after being linked with a move to Serie A clubs[43] and Watford.

[47] Kuzmanović made his Basel debut in the opening game of the season, where he came on as a substitute for Delgado in the 63rd minute, in a 2–1 win over Vaduz.

[48] Kuzmanović suffered an injury when he tore his muscle in his right thigh, in a 3–1 win over Thun on 12 August 2015 and was sidelined for four weeks.

[50] With his first team opportunities limited, Kuzmanović was linked with a move back to Serie A, with Genoa, Bologna and Sampdoria and was expected to leave the club in the January transfer window.

[56] Since his return, Kuzmanović became a first team regular in midfield position, which he enjoyed playing[57] and went on to make sixteen appearances, for the club.

[60] He made his Málaga debut in the opening game of the season, coming on as a 71st-minute substitute for goalscorer Juanpi in a 1–1 home draw against CA Osasuna.

[65] In early 2007, Serbian FA began talks with him about the possibility of playing for the Serbia national team[66] and he accepted the call up to the squad against Kazakhstan and Portugal in March 2007.

[71] He earned a total of 50 caps (6 goals)[72] and his final international was a November 2014 European Championship qualification match against Denmark.