After playing with the junior youth clubs of Aris, Kalaitzakis began his professional career in 2016, with the Greek club Panathinaikos. With Panathinaikos, he won the Greek Cup title in 2016, 2017, and 2019, and also the Greek League championship, in 2017, 2018 and 2019.
In March 2018, Kalaitzakis announced his intention to declare for the 2018 NBA draft.[1] He later withdrew from the draft before the draft's withdrawal deadline.
Nevėžis (2019–2020)
On August 28, 2019, Kalaitzakis signed with Nevėžis Kėdainiai of the Lithuanian Basketball League, on a loan deal from Panathinaikos.[2] In 23 games played in the Lithuanian league's 2019–20 season, he averaged 12.2 points, 4.3 rebounds, 2.3 assists and 1 steal in 28.7 minutes per game.[3]
In April 2020, Kalaitzakis declared for the 2020 NBA draft.[4] However, he withdrew before the draft took place.
Kalaitzakis was selected by the NBA's Indiana Pacers, with the 60th overall pick of the 2021 NBA draft. His draft rights were then traded to the Milwaukee Bucks, along with the draft rights of the 54th pick, Sandro Mamukelashvili, and two second round draft picks, for Isaiah Todd.[7] Kalaitzakis' contract with Panathinaikos had a buyout amount of $300,000, which was paid by the Bucks.[8]
On August 11, 2021, the Milwaukee Bucks announced that they had signed Kalaitzakis.[9] Kalaitzakis made his debut in the NBA on October 19, 2021, coming-off from bench with two rebounds in a 127–104 win over the Brooklyn Nets.[10] On December 3, he was waived by the Bucks after nine appearances.[11]
Oklahoma City Thunder / Blue (2021–2022)
On December 30, 2021, Kalaitzakis was claimed off waivers by the Oklahoma City Blue of the NBA G League[12]
where he played in 31 regular season games and averaged 10.1 points, 3.9 rebounds and 2.1 assists in 19.6 minutes per game.[13] On April 5, 2022, he signed with the Oklahoma City Thunder for the rest of the season.[13] Kalaitzakis played four games for the Thunder, averaging 41.5 minutes and 17.5 points per game.[14]
Second stint with Panathinaikos (2022–2023)
On July 25, 2022, Kalaitzakis signed a two-year contract with Panathinaikos, returning to Greece and reuniting with his twin brother Panos.[15] In 26 EuroLeague games (16 starts), he averaged 2 points and 1.1 rebounds in 10 minutes per contest. Additionally, in 29 domestic league matches, he averaged 6.4 points, 1.8 rebounds and 1.2 assists in 13 minutes per contest.
On September 4, 2023, Kalaitzakis was released from the Greek powerhouse.
Kalaitzakis' twin brother Panos[19] is a professional basketball player and had been Georgios' teammate in both the Lithuanian club Nevėžis Kėdainiai as well as Panathinaikos. Their younger sibling Alexandros (born 2003) also plays basketball professionally.[20]