Barca have agreed a two-year deal with Depay, who becomes the club’s third signing on a free transfer this summer after moves for Sergio Aguero and Eric Garcia had already been confirmed.
They have also paid nine million euros to activate a clause to recall right-back Emerson from Real Betis.
Depay has long been a key target for Barcelona coach Ronald Koeman, who worked with the player when he was in charge of the Dutch national team.
Koeman was in the crowd in Amsterdam on Thursday to see Depay score an early penalty for the Netherlands in their 2-0 victory over Austria at Euro 2020.
The 27-year-old was reportedly close to sealing a 25-million-euro move to Barca last year while a reduced fee was also mooted in January, but the club decided to wait for his contract to expire.
“The player will sign a contract until the end of the 2022-23 season,” the club’s statement read.
He will likely compete with Sergio Aguero for the central striker position as Koeman looks for more of a physical presence up front.
Barcelona’s financial problems mean the club are expected to sell a number of fringe players this summer. Philippe Coutinho, Samuel Umtiti and Miralem Pjanic are among those likey to leave.