He debuted for the senior team of Žalgiris Kaunas on 22 January 2017 against Nevėžis Kėdainiai.

[1] In June 2017, he participated in adidas Eurocamp in Treviso, and led Europe to an 82–62 victory over the United States, scoring 16 points and grabbing 4 rebounds.

[5] On July 2, 2022, Masiulis signed with Rytas Vilnius of the LKL and the Basketball Champions League.

[6] Gytis Masiulis made his youth debut for Lithuania at the 2014 FIBA Europe Under-16 Championship in Latvia.

[10] Gytis is the son of former Lithuanian national basketball team member Tomas Masiulis, who won a bronze medal at the 2000 Summer Olympics in Sydney, and previously had success with Žalgiris Kaunas and Prokom Trefl Sopot in the EuroLeague.