After three seasons with Željezničar, he moved abroad for the first time in his career, signing a 4-year contract with Polish club Lech Poznań in June 2008.

[4] On 23 July 2012, Štilić joined Karpaty Lviv,[5] He stayed in Ukraine for only one season, as he left for Turkish club Gaziantepspor in August 2013.

[11] On 26 August 2015, Štilić scored from a long-range free kick against Astana at the GSP Stadium, in APOEL's 1–1 draw in the play-off round of the 2015–16 UEFA Champions League.

[18] He was named man of the match in Željezničar's 3–1 away league win against Sarajevo in the derby on 30 November 2019, scoring two goals and earning an assist.

[2][3] Štilić made his senior international debut for Bosnia and Herzegovina on 30 January 2008, in a friendly game against Japan, coming on as an 83rd-minute substitute in 0–3 away defeat.