The former Middlesbrough attacker failed to become a consistent starter for the Blaugrana after his arrival as an emergency signing in 2020 and was pushed down the pecking order by the signings of Pierre-Emerick Aubameyang and Robert Lewandowski.
Braithwaite has not been a part of Xavi's plans early in the 2022-23 season and was the subject of boos by supporters ahead of the Joan Gamper Trophy win over Pumas last month.
The 31-year-old was initially believed to be refusing to terminate his contract at Camp Nou - which ran until 2024 - but La Blaugrana have now confirmed that he has left the club.
"FC Barcelona publicly expresses its gratitude to Braithwaite for his commitment and dedication and wishes him the best of fortune and every success in the future," a statement read.
Braithwaite leaves Barcelona after registering 10 goals and five assists in 58 matches for the club in all competitions, and he is now expected to complete a free transfer to Espanyol.
The Denmark international is not expected to be the only striker to leave Barcelona on transfer deadline day, as ex-Arsenal man Aubameyang prepares to return to the Premier League with Chelsea.
Aubameyang has also lost his place in the starting XI to old Bundesliga rival Lewandowski and is expected to sign for the Blues on a two-year deal with the option of a further 12 months.
The 33-year-old was subjected to a horrifying burglary at his home at the weekend, which left him with a broken jaw, but the incident is not expected to jeopardise his move to Stamford Bridge.
In exchange for the sale of Aubameyang, Barcelona will supposedly receive €14m (£12.1m) and left-back Marcos Alonso from Chelsea, and the striker will soon arrive in the UK to complete his switch.
Aubameyang amassed 68 goals and 16 assists in 128 Premier League outings during his Arsenal career and ended his first half-season at Barcelona with 13 goals from 23 appearances in all competitions.
Braithwaite and Aubameyang would follow the likes of Oscar Mingueza, Dani Alves, Rey Manaj, Ferran Jutgla, Riqui Puig and Neto out of the Barcelona exit door, while Samuel Umtiti and Clement Lenglet have left on loan.
Right-back Sergino Dest is also expected to depart before the deadline, as AC Milan close in on the loan signing of the USA international.