The young custodian has committed his future to the Rojiblancos despite being a bit-part player at the club in the 2011-12 campaign
The 22-year-old joined the Rojiblancos in 2009 and was billed as one of the most promising shot-stoppers in the country, but a series of injuries have hindered his progress.
Asenjo found himself behind Thibaut Courtois in the club's pecking order this season, but with an extension to the Belgian's loan not yet guaranteed, Atletico have tied down the former Spain Under-21 international until 2016.
"I am happy to see that Atletico are still betting on me," Asenjo said. "Both parties are happy with this and very eager to continue this relationship."
Asenjo made five competitive appearances in 2011-12 for Atleti, who finished in fifth place in La Liga.