Lucas joined São Paulo FC in 2005 after playing for the youth teams of Clube Atlético Juventus and Corinthians. Lucas made his debut with the São Paulo first-team in 2010, scoring 4 goals and providing four assists in 25 appearances. In 2011, Lucas scored nine goals and provided four assists in 28 appearances in the Campeonato Brasileiro and 13 goals and eight assists in all competitions.
During the Summer of 2012, both Manchester United and Inter Milan were reported to be interested in signing Lucas. On 8 August 2012, Paris Saint-Germain won the battle and announced the player would be moving to the club in January 2013. There was strong speculation that his father was offered a bribe by Paris Saint-German to persuade his son to join the club, however, it was later discovered that the rumors were false. He would be the club's most expensive signing. The transfer fee was reported to be in the region of €45m (€44.3). It has also been announced that Lucas will wear the No. 29 shirt for the remainder of the season. On 11 January 2013 Moura made his debut against AC Ajaccio, but the match ended a 0–0 draw. He also played in the UEFA Champions League away at Valencia; PSG won the game 2–1, with Lucas assisting a goal.