Finding Dory will focus on the absent-minded, chatty and blue tang fish voiced by comedian Ellen DeGeneres, who was a big hit with audiences.
"I'm excited that it's finally happening," DeGeneres said on her daytime talk show, Ellen.
"I read the script and it's fantastic, it's hilarious, it's warm, it's everything that you want it to be," she added.
"There is no Dory without Ellen," Stanton said in a statement. "She won the hearts of moviegoers all over the world – not to mention our team here at Pixar."
The film is set for a November 25 2015 release, the day before the US Thanksgiving holiday that coincides with the start of the holiday film season.
Speculation about a Finding Nemo sequel has floated ever since it became a top-grossing animated film. It took in some $922-million at worldwide box offices, ranking fourth among animated films, according to box office tracker website BoxOfficeMojo.com.
Finding Nemo won the Academy Award for best animated feature in 2004, and was also nominated for three other Oscars.
Disney-Pixar is a subsidiary of Walt Disney. – Reuters