Robert Lewandowski on Sunday crowned his 34th birthday with his first competitive goals for Barcelona when club faced Real Sociedad.
The summer signee from Bayern Munich scored two goals within the first minute and 68th minute of the game.
His first goal was assisted by Balde MartÃnez, and the second Fati Vieira.
Barcelona scored four goals whereas Real Sociedad managed to secure a goal.
Ousmane Dembele secured the second goal while Ansu Fati added the fourth.
The handsome victory was welcome following Barca’s modest start to their campaign – a 0-0 draw at home to Rayo Vallecano.
Lewandowski joined Barca in the summer in a £42m deal from Bayern, where he only had one year left on his contract, while another of their new signings, Brazil’s ex-Leeds United forward Raphinha, came on as a second-half substitute.
However, Barcelona were unable to field France central defender Jules Kounde as he has still not been registered because of financial reasons following his transfer from Sevilla at the end of July.
Barca are fifth in La Liga and play Manchester City in a friendly on Wednesday, with their next competitive game against Valladolid at the Nou Camp on Sunday.