The 31-year-old actress, last year's winner, was presenting the best actor in a supporting role Oscar, which was won by JK Simmons for his role in "Whiplash".
Before announcing Simmons' name, Nyong'o said, "The actor goes to". She quickly corrected herself saying, "Sorry, the Oscar goes to."
Nyong'o's was the first flub of the awards ceremony, which saw host Neil Patrick Harris ditch his clothes and don a white underwear on stage.
