[4] He played the whole game in Dinamo's 4–2 win on penalty kicks over RNK Split in the 2015 Croatian Cup Final on 20 May 2015.

[7][8] An ankle injury shortly afterwards and the team's erratic form, however, hindered Šimunović's attempts to make much impact at his new club.

[18] Šimunović re-established himself in the team, and formed a solid partnership in central defence alongside Erik Sviatchenko which saw Celtic go on a run of nine clean sheets.

[32] In September 2015, he received a first call-up for the senior national team, for the last UEFA Euro 2016 qualifying matches, against Bulgaria and Malta, as a substitute for injured Dejan Lovren, but suffered an injury days later, which prevented him from playing.

[36] He was called up a month later by Bosnia and Herzegovina coach Mehmed Baždarević for the 2018 World Cup qualifiers against Cyprus and Gibraltar; however, he did not debut for the national team despite being expected to do so against the latter opponent.

[37] In March 2018, he rejected the call-up from new Bosnia and Herzegovina coach Robert Prosinečki for friendly games against Bulgaria and Senegal.

[39][40] In April 2023, having been released by HNK Gorica, Šimunović told a Scottish newspaper that he was studying sports management at a university in Croatia and was doing his badges to prepare for a career after his playing days were over.