The Danish player will join the Catalans for his €18m buy-out clause, and he said goodbye at the club offices this afternoon, meeting president Maria Pavon and staff.
Braithwaite, 28, will sign a contract until the summer of 2023. He arrives at the direct request of coach Quique Setien, who preferred him to the other option, Getafe's Angel Rodriguez.
The coach, who has been handed a small squad since replacing Ernesto Valverde, wanted a more versatile player. He believes Braithwaite is capable of playing across the front three.