The 29-year-old Denmark international had failed to find the back of the net in his three previous appearances for the Spanish champions after joining the club from Leganes in February, shortly before the season was suspended because of the coronavirus pandemic.
The former Middlesbrough striker was brought in as an emergency signing after injuries to Luis Suarez and Ousmane Dembele depleted the Barcelona frontline.
After Arturo Vidal’s opener, Braithwaite opened his Barcelona account in the 37th minute before further goals from Jordi Alba and Lionel Messi took Quique Setien’s men five points clear of Real Madrid, who host Eibar on Sunday.
"I've been waiting for it for a long time, so it's amazing to score my first goal,” Braithwaite said after the game.
"It was most important to start like we did [on Saturday], so we are happy and we have to continue like this.
"As an offensive player you want to score goals and I've been working a lot in this break, and I've been really looking forward to playing this game and hopefully getting a goal and I'm happy, I'm really happy."
"It's really important because we have to start with confidence, and to score four goals and not concede any goals is really important for us.
"We started good and just built our confidence and we need that to continue pursuing what we want."
Barcelona will return to action with a home game against Leganes on Tuesday.
