The 20-year-old joined Atletico from Independiente in the summer of 2006 for £15million.
Aguero has scored 14 times for Atletico so far this season.
“The club reached an agreement with IMG, the company that manages me, to extend my contract until 2012.” he told Uefa’s official website.
“I know they will work together on the exploitation of my image rights, there’s a good understanding between the parties.
“All the signs are that I will stay here for a long time, and I’m really happy about that.
“I’m enjoying it here and I never want to leave, because Atletico was the first club to welcome me in Europe.”