Espanyol had won on their last two visits to Bilbao and were unbeaten in seven meetings between the sides.
However, Sergio's men were second best on this occasion as Aduriz, back from a short lay-off with a hamstring injury, enjoyed a successful return to action.
The experienced striker scored one goal and set up another to put Athletic in control at the break, before Ander Iturraspe rifled home a superb third from distance with 12 minutes remaining.
Iturraspe's strike put the result beyond doubt and Victor Sanchez's 84th-minute reply represented little consolation for an Espanyol side that remains just two points above the bottom three.
Athletic enjoyed the better of the first half and came close to claiming an early lead when a left-wing corner from Markel Susaeta flicked off an Espanyol head and drifted narrowly wide of the far post.
Another Susaeta corner led to the opener in the 29th minute, as Aduriz escaped the attention of Espanyol's defenders to head goalwards from 12 yards. His effort deflected off Christian Stuani and left Kiko Casilla - who made his debut for Spain in the recent international break - helpless.
Casilla was fortunate not to concede a penalty when he clattered Aduriz on the left of the area, but another Athletic goal arrived with a minute of the first period remaining.
Aduriz slipped a perfectly weighted through ball into the path of Borja Viguera, who prodded an instinctive first-time shot past Casilla with the outside of his right boot.
When Iturraspe fired in a 25-yard strike off the inside of Casilla's left-hand post, there was clearly no way back for Espanyol.
However, Sanchez at least got the visitors on the scoresheet when he converted a cutback from substitute Salva Sevilla.
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