Leko's career began with GNK Dinamo Zagreb in 2000 in his native Croatia, although he was not an immediate success. After spending some time on loan at NK Croatia Sesvete, he became a regular starter in 2001/2002, helping Dinamo Zagreb win the Croatian Cup, scoring in the final against NK Varteks and being named Man of the Match. Leko eventually moved to Dynamo Kyiv in 2002 for €5.5m. In his first season in Ukraine, Dynamo won the double, with Leko playing 18 times. In February 2006, it was announced that Leko would be leaving Dynamo Kyiv, having turned down a new contract offer. He subsequently signed for AS Monaco on a free transfer on 4 June 2006. In July 2009, The Times reported that he had turned down a move to English Premiership club Wolverhampton Wanderers as they would not meet his wage demands of 30,000 UK pounds per week net. On 18 June 2010 Bucaspor signed the Croatian midfielder to a two-year deal on a free transfer from AS Monaco. On 25 May, it was confirmed that Leko signed a two-year deal with GNK Dinamo Zagreb. In August 2014 he moved to NK Lokomotiva on loan. In 2015, he permanently joined Lokomotiva for the last season of his professional career.
International career
Leko made his Croatia debut in 2002 against Hungary, but was not included in the 2002 World Cup squad. He scored a goal in a 4–0 victory against Belgium in a Euro 2004 qualifier, and was included in the final stage's squad, but only played 22 minutes during the tournament. Selected to represent the nation in the 2006 World Cup, Leko made two substitute appearances, against Brazil and Australia. He was also part of the final squad for Euro 2008. 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. However, officiating referee Roberto Rosetti disallowed the substitution from occurring as he also allowed Turkey an extra 2 minutes to find a late equalizer to send the game to a penalty shootout which Turkey eventually won.
