"[Expletive] stole my seat," she jokingly confirmed to host Jimmy Kimmel.
Streep said she returned from a break to find Carey sitting in her spot and "sucking up" to Spielberg. Carey explained she was told to sit down and offered to move, which Streep said she initially declined.
"'No, no stay there. I'll sit on your lap because... comfy!'" she recalled of her response.
Carey had said Sunday on Twitter that she accidentally took Streep's seat while on her way to the restroom.
"Got caught mingling on the way to the loo during a commercial break.. took the first available, happens to be right next to Steven Spielberg. Cut to next commercial break, guess who comes back to her seat..." the singer wrote.
"(me) Dear Meryl, please forgive me!!! (MERYL STREEP) You can take my seat any time!" she added.
Streep and Carey were nominated at the awards show for Best Actress in a Motion Picture - Drama and Best Original Song, respectively. Streep lost to Frances McDormand, while Carey lost to Pasek & Paul.