Barcelona says it paid PSG 16.5 million euros ($18.3 million), with another 4 million euros depending on results, for the 22-year-old Digne.
Digne’s transfer comes a day after the Spanish champions agreed to sign France central defender Samuel Umtiti.
Digne played for AS Roma on loan last season. He was included on France’s squad for this year’s European Championship, but didn’t play.
He and Umtiti will help rebuild Barcelona’s back line after the departures of Dani Alves and Marc Bartra.
Barcelona has also signed Denis Suarez from Villarreal.