The striker guided the ball home from inside the area to give last season's Europa League runners-up just their second league win of the campaign.
Osasuna, in the bottom three, could count themselves desperately unfortunate not to have taken something from the game as they hit the bar twice and a post once, but the hosts rode their luck.
Athletic went in front after 12 minutes when Oscar De Marcos' ball in from the right picked out Aduriz and his finish found the bottom-right corner.
Aduriz almost added another midway through the first half, but his header from a Markel Susaeta corner went over.
The visitors took drastic action to get back into the match, making a double substitution after only half-an-hour with Francisco Punal and Roland Lamah replacing Anthony Annan and Sisi.
Lamah had an instant impact as he crashed a shot against the bar and the woodwork came to Athletic's rescue again two minutes later, Lolo's 30-yard free-kick also coming back off the bar.
The visitors, with just one win to their name this season, continued to press for an equaliser after the break and Joseba Llorente brought a save from Gorka Iraizoz.
At the other end De Marcos' shot was blocked by visiting keeper Andres.
The hosts continued to live dangerously, though, a David Timor free-kick from the left edge of the area coming back off the post.
Iraizoz then held a Lamah header with two minutes remaining but Athletic held on to claim a timely victory.