He first began practicing gymnastics at age three and was briefly a part of the youth setup of HAVK Mladost, a waterpolo club based in Zagreb.

[11] Valent was forced to miss part of the 2015 season with a rib injury and the brothers did not compete at the European championships.

[13] The two brothers continued competing in the coxless pair in the 2019 European Rowing Championships as well, holding the leading position throughout the race, and finishing first with a time of 6:22.46.

[15] Together with David Šain, Damir Martin and his brother, he participated in the 2012 Summer Olympics in London, in the quadruple sculls event.

However, the German representatives would hold almost a boat lengths lead in the final race, with the Croatian team just barely winning the silver medal, as the Australians finished close behind.

In the final race of the event, the brothers held a narrow lead over the Lithuanian representatives, who overtook them by the 1500 meter mark.

[19] Sinković competed in the 2020 Summer Olympics in Tokyo, entering the coxless pair event with his brother Valent.

The pair entered the final race as overwhelming favorites to win the gold medal, with a betting coefficient of 1,03 and won with a time of 6:15.29.

[24] The same team competed in the 2013 World Rowing Championships, in the same category, finishing with a time of 5:53.57 and winning the gold medal.

[30] Valent and his brother Martin Sinković competed in the double sculls event of the 2022 World Rowing Championships.