The Ligue 1 club have released a statement confirming that the Argentina international has signed a four-year contract with the club.
Lavezzi, 27, will wear the number 11 shirt at PSG at Parc des Princes having completed a medical on Monday.
"PSG gave me the opportunity to grow and I think they will become one of the most powerful clubs," Lavezzi said. "I stayed very quiet during all these weeks. I knew it was very solid. I took my vacation.
"I do not think Italian football is in crisis. This is a very competitive league. I came here because there is a real project and the opportunity to win things. I'll try and do what I did in Naples."
The transfer is worth an estimated 30 million euros (£24.1 million) and underlines PSG's intent to compete at the very top level of European football.
Lavezzi was one of the key figures in a Napoli team that played in the Champions League last season and at times threatened to disrupt the established order in Italian football.
The forward scored 38 goals in five seasons in Serie A following a move from San Lorenzo to the Naples club in 2007.
Sporting director Leonardo said: "We still have the idea of improving the personality and mentality of the group. A player like him raises the level of others. I think it will mark the club's history."