Marinovic attended Auckland private school, Kings College. In 2005, he won the Under 15 New Zealand National Championships. In 2008, Marinovic was selected for the New Zealand Under-19 Schoolboys National Team for its tour of Austria. He received trials from clubs such as Everton FC, FC Zürich and FC Schalke 04, but they all failed. So he joined Waitakere United, he reached the final of the national championships again, but this time lost 6-0 to Canterbury United.
In the mid-2009 he was a graduate of the Wynton Rufer Soccer School of Excellence, created for young footballers to have the chance of a trial at Hamburger SV or SV Werder Bremen. There he was spotted by SV Wehen Wiesbaden and he signed a professional contract with them. He was the 3rd choice goalkeeper in the 2010/11 season, and played with the U23 team.
He made his professional debut for Wiesbaden on 27 April 2010 in an away game to league leaders Erzgebirge Aue when Marc Birkenbach was injured after 30 minutes. The game finished 2-2. When Michael Gurski was signed, he again became the 3rd choice keeper, only being used for the U23 team.
In 2013, Marinovic left Wiesbaden and joined FC Ismaning and then 1860 Munich Reserves, making one appearance at each club. In 2014, Marinovic signed with German 3rd division and now 4th tier club, SpVgg Unterhaching.
On 21 July 2017, Marinvoic signed with Canadian MLS side Vancouver Whitecaps FC.
In 2011 Marinovic travelled with the New Zealand under-20 side to the World Cup in Colombia where he made two appearances.
On 8 March 2015, Marinovic was called into the New Zealand national football team to play a friendly against South Korea by coach Anthony Hudson. He made his debut in the match in Seoul on 31 March, playing the full 90 minutes. He conceded a penalty kick, but saved it, conceding the only goal of the game by Lee Jae-sung in the 86th minute
On 11 June 2016, Stefan Marinovic saved two penalties in a 4–2 shootout win against Papua New Guinea in the OFC Nations Cup final after a 0–0 draw after extra time.New Zealand
OFC Nations Cup: 2016
OFC U-20 Championship: 2011
OFC Nations Cup Golden Gloves: 2016