Barcelona made it two wins from two in LaLiga as Raphinha proved the difference at the Nou Camp.
The Brazil forward ran on to a superb pass from Pedri to slot in the opener and show again he is capable of filling the central attacking role for Barca this season.
Raphinha was flanked by Lamine Yamal and England’s Anthony Gordon, who went close to his first goal in LaLiga in the second half but saw his shot deflected wide.
Lamal went even closer, smashing the crossbar from range.
Barca introduced former Manchester City man Rodri for his debut in the second half as the hosts controlled the match.
Nico Williams provided Athletic’s main outlet on the break, but Hansi Flick’s high backline limited clear-cut chances on Joan García’s goal.
And Barca found a late second when Fermin Lopez stole in to smash home after Karim Adeyemi’s cross had caused havoc.
It’s now 20 home league wins in a row for Barca – who host Rayo Vallecano on Monday night.