Born in Klaipėda, Mikalauskas started his career with his hometown team Neptūnas and the Vladas Knašius Basketball School.
In 2019, Mikalauskas signed with Dutch side Aris Leeuwarden.[1] He averaged 12.8 points and 8.1 rebounds before the season was cancelled due to the COVID-19 pandemic. With Aris, he also reached the final of the NBB Cup, which was never played.
In the 2020–21 season, Mikalauskas played with Feyenoord Basketball.[2] This became his breakout season as he averaged 18.1 points and 7.1 rebounds per game while leading Feyenoord to a fifth place. After the regular season, Mikalauskas was named to the All-DBL Team.[3]