He joined Peñarol in Uruguay in 1933. After one year, he came back to Brazil to play for Vasco da Gama. He helped them win the Rio State Championship. After playing in the World Cup in 1934 he joined Botafogo and won another Rio State Championship in 1935. The following year, he joined Flamengo, where he stayed until 1941. Once again, in 1939, the team won the Rio State Championship. He was also at the forefront of the movement against prejudice in football, being one of the first black players to join the then-elitist Flamengo team.
Leonidas joined São Paulo in 1942 and stayed at the club until his retirement from playing in 1950.
Leônidas is one of several possible players credited for inventing the "Bicycle kick". The first time Leônidas used this technique was on 24 April 1932, in a match between Bonsucesso and Carioca. In Flamengo he used this move only once, in 1939, against the Argentinian team Independiente. The unusual volley gained huge fame at the time, propelling it into the football mainstream. For São Paulo he used the bicycle kick on two occasions: the first on 14 June 1942, in the defeat against Palestra Italia (currently Palmeiras). Most famously of all, he used it on 13 November 1948, in the massive 8–0 victory over Juventus. The play (and the goal) was captured in an image  and is regarded as the most famous picture of the player. In the 1938 World Cup, he also used the bicycle kick, to the delight of the spectators. When he did it, the referee was so shocked by the volley that he was unsure whether it was within the rules or not.
He played 19 times for the Brazilian national team, scoring 21 goals in total, and scoring twice on his debut. In 1938, he was the World Cup's top scorer with 7 goals, scoring at least three times in the 6–5 extra time win over Poland. Brazil manager Adhemar Pimenta decided to rest him for the semi-final against Italy. The Italians won the game 2–1.
He joined São Paulo as manager in 1953, before leaving football to become a radio reporter and then the owner of a furniture store in São Paulo. Leônidas died in 2004 in Cotia, São Paulo, because of complications due to Alzheimer's disease, from which he had been suffering since 1974. He is buried in the Cemitério Morada da Paz of São Paulo.