The musical, set to take place June 4 at the Hollywood Bowl in Los Angeles, will feature Bareilles in the title role as Ariel with Wilson set to star as the evil Ursula.
Backed by a full orchestra, the singer and actress will be joined by Glee star Darren Criss as Prince Eric, Unbreakable Kimmy Schmidt's Tituss Burgess as Sebastian, John Stamos as Chef Louis and Scandal actor Norm Lewis as King Triton.
"I suppose this is the part where I say, 'Dreams do come true,'" Bareilles said in a statement. "I am truly honored and excited beyond words to be a part of a performance of one of my favorite scores and stories of all time. I've been pretending I was Ariel in swimming pools since I was a little girl, and now I get to pretend on a bigger stage. This is just fantastic."
Wilson added how she hopes to make the original voice actress from the Disney animated version of The Little Mermaid proud with her portrayal of Ursula. "I hope to do the amazing Pat Carroll proud by performing Ursula's song," she said. "It's just such a delicious role that I've always wanted to play."
Tickets for the performance go on sale April 9.