Finding Dory is set to hit cinemas internationally in November 2015, with Ellen DeGeneres, Alexander Gould and Albert Brooks all returning to the ocean.
"I have waited for this day for a long, long, long, long, long, long time," DeGeneres said in a statement when the sequel was announced.
"I'm not mad it took this long. I know the people at Pixar were busy creating Toy Story 16. But the time they took was worth it," she joked.
"The script is fantastic. And it has everything I loved about the first one - it's got a lot of heart, it's really funny, and the best part is... it's got a lot more Dory".
DeGeneres voiced the part of Dory, the loveable and forgetful sidekick to Nemo's (Gould) father Marlin (Brooks) for the first film 10 years ago.
The original 2003 film, which grossed over €700 million, was recently re-released on 3D across UK and Ireland.
"There is no Dory without Ellen," director Andrew Stanton said.
"She won the hearts of moviegoers all over the world - not to mention our team here at Pixar.
"One thing we couldn't stop thinking about was why she was all alone in the ocean on the day she met Marlin.
"In Finding Dory, she will be reunited with her loved ones, learning a few things about the meaning of family along the way."