The 29-year-old scored 18 Ligue 1 goals last season, but failed to make France's final Euro 2016 squad.
Ben Arfa joined Nice after having his contract terminated by Newcastle, whom he joined in 2010, and following a loan spell at Hull City that was cut short.
He has signed a two-year deal with the French champions, who are planning for life without Zlatan Ibrahimovic.
PSG will go into next season without leading scorer Ibrahimovic, who is expected to sign for Manchester United, and with a new manager after Unai Emery replaced Laurent Blanc.
Ben Arfa scored 13 goals in 76 games for Newcastle after joining from Marseille, initially on loan before making it permanent in 2011.
He failed to score in nine appearances on loan at Hull in 2014/15.
Paris St-Germain have signed Hatem Ben Arfa on a free transfer after his contract ran out at Nice.