The Ligue 1 outfit reportedly agreed a fee of €35m for the highly-rated player over the summer, but they allowed the the 20-year-old to remain with Sao Paulo for the remainder of their season.
But with the Brasileirao set to conclude this weekend and O Tricolor Paulista already guaranteed fourth place, Lucas can start turning his attentions towards his move to the capital club in January.
"I am leaving Brazil for a great opportunity abroad offered to me by Paris Saint-Germain," he said. "A footballer needs to seize moments like these, you'll never know what tomorrow is going to bring.
"I have goals to achieve in Europe, and PSG are a massive club. They made a proposal that was good to me and to Sao Paulo. There are a lot of Brazilian players at PSG and the club have an excellent project. These factors made me reach a decision."
"I have always enjoyed watching skilful players such as Robinho, [Lionel] Messi, Denilson and Ronaldinho. Those guys had a fantastic touch and I studied them a lot so I could try to emulate some of their moves, copy some of their skills."