Leonidas Kaselakis was born in June 1, 1990 and he is a 2.02m forward. He began his professional career in the Greek Second Division with Ilysiakos. He signed a two-year contract with the Greek First Division club, PAOK, in 2012 and in 2014 he moved to AEK Athens.
He was named the Greek League Most Improved Player in 2016 as a player of Kifisia. On July 17, 2016, Kaselakis signed with the Kazakh VTB United League team Astana. He played there for 2 years and he won 2 Championships and 2 Cups.
Kaselakis returned to Greece and signed a two-year contract with Promitheas Patras on June 27, 2018.
As a member of the junior national basketball teams of Greece, Kaselakis won the gold medal at the 2008 FIBA Europe Under-18 Championship and the silver medal at the 2009 FIBA Under-19 World Cup. He also won the gold medal at the 2009 FIBA Europe Under-20 Championship and the silver medal at the 2010 FIBA Europe Under-20 Championship with Greece's junior national team.
Kaselakis first became a member of the senior Greek national basketball team in 2018. He played at the 2019 FIBA World Cup qualification.