The awards presentation will honor the best films of 2012. It will be held next February.
Fallon has long been rumored to be in the running to serve as emcee of the star-studded event. Billy Crystal was the host of this year's show.
However, Fallon said on Wednesday's edition of the "Today" show he has declined the gig.
"No, I'm not going to do the Oscars," Fallon said on "Today," which is taping in London for the Olympics. "It's an honor to be asked by the Academy [of Motion Picture Arts and Sciences,] but it's not my year."