The actress voiced Dory, a Pacific Regal Blue Tang who suffers from short-term memory loss. Plot details for the new film are being held under wraps.
Andrew Stanton is directing the sequel from a script provided by Victoria Strouse. Lindsey Collins will be producing.
The original is the highest grossing film for Pixar, bringing in $868 million worldwide. It also won the Academy Award for Best Animated Feature.
Finding Nemo is returning to the big screen in 3D on September 14th.