After spending some time on loan at Croatia Sesvete, he became a regular starter in 2001–02 season, helping Dinamo win the Croatian Cup, scoring in the final against Varteks Varaždin and being named Man of the Match.

In July 2009, The Times[2] reported that he had turned down a move to English Premier League club Wolverhampton Wanderers as they would not meet his wage demands of £30,000 per week (approx.

At the tournament quarter-final clash between Croatia and Turkey, Leko was supposed to make his first appearance in the competition as a late substitute as Slaven Bilić wanted to put him on to hold on for a Croatian victory.

[5] Leko started his managerial career by succeeding Besnik Prenga on the bench of Lokomotiva's U19s in the summer of 2017, leading them through 2017–18 UEFA Youth League.

[7] On 5 January 2021, he succeeded Boris Perković on the bench of Hrvatski Dragovoljac, who held first place on the Druga HNL table at the time of his hiring.

[8][9] However, on 9 January 2021, just four days after the appointment at Hrvatski Dragovoljac, Leko left the club and succeeded Goran Tomić as the head coach of Lokomotiva in the Prva HNL.