Aduriz plans to retire at season's end but the 38-year-old Bilbao star showed he still has plenty of football left in the tank thanks to his unforgettable 89th-minute winner on Friday.
The club great scored within a minute of his introduction via a spectacular overhead kick against the La Liga champions at San Mames.
The Spanish striker, who played for the club three separate times throughout his career, has been with Athletic Bilbao since 2012 and has scored 172 goals in 391 games.
Aduriz's goal saw him match a Lionel Messi scoring feat, having now scored in 15 consecutive seasons in Spain's top flight, and the veteran striker revelled in the result.
Athletic Club (@AthleticClub) August 16, 2019
"The team has been amazing," Aduriz told reporters. "There is no better way to start than by adding three points against Barca.
"I said I was going to be there to help Athletic until the last day and today I have been able to prove it.
"The atmosphere of San Mames is always insurmountable, but it is true that today people have taken this game even more eagerly.
"Athletic's base is young people. You have to give them confidence and go slowly with them. They will help us a lot throughout the year."
"Dedicated to my family and everyone who supports me," Aduriz said of the goal. "These kind of things make football so beautiful."
"Everything in life has a start and a finish. I'm grateful to be able to choose to end things where I'm happiest," he continued.
Inaki Williams, who signed a nine-year contract extension with Bilbao following links to Manchester United, added: "I am very happy for Adu.
"It's his last season and I want him to say goodbye with as many goals as possible."
Athletic Bilbao will face Getfe in their next match while Barcelona will look ahead to a clash with Real Betis.