Career
He started playing football at age of 7 in his village, Gornja Lomnica. At the age of 12 he joined Dinamo Zagreb from Hrvatski Dragovoljac. Dinamo Zagreb
He made his debut for Dinamo Zagreb on 16 March 2013 against Istra 1961, coming as a 90th-minute substitute.
On 30 March 2013, he scored his first goal for Dinamo Zagreb against Zadar in the 34th minute.
In the 2013/14 season he helped Dinamo to their 9th League title in a row, making 32 appearances in all competitions, and made it 10-in-a-row in 2015, where he made 30 appearances in all competitions. Celtic
On 1 September 2015, Šimunović joined Scottish Premiership side Celtic for an undisclosed fee.
He made his debut on 17 September, playing in Celtic"s 2–2 draw away against Ajax Amsterdam in the Europa League. He has been capped at U14, U15, U16, U17, U18, U19, U20 and U21 level for Croatia scoring 3 goals, against Germany for the U15"s, Austria for the U17"s and Norway for the U21"son
He was captain of the Croatia U17 and the Croatia U19 teams and is current captain of the Croatia U21 team
In September 2015, he received a first call-up for the senior national team, for the last Euro 2016 qualifying matches, against Bulgaria and Malta, as a reserve player for already injured Dejan Lovren, but Šimunović has suffered a small injury days after the call-up, removing him for the games against Bulgaria and Malta. Dinamo Zagreb
Croatian First League: (3) 2012-2013, 2013-2014, 2014-2015
Croatian Cup: (1) 2015
Croatian Super Cup: (1) 2013
Croatian U19 League: (1) 2010-2011
Croatian U17 League: (2) 2008-2009, 2009-2010.