He was released by Aris on 15 July 2018, and he later joined the newly promoted to the first-tier Greek League team of Holargos.

On 2 July 2022, Kalaitzakis signed a three-year (2+1) deal with Panathinaikos of the Greek Basket League and the EuroLeague.

[5] On 25 January 2024, Kalaitzakis recorded his highest-scoring EuroLeague game, with 17 points against Maccabi Tel Aviv.

Kalaitzakis played with the senior Greek national team at the 2023 FIBA World Cup qualifiers.

His twin brother, Georgios, as well as their younger sibling Alexandros (born 2003), are professional basketball players.