The actor revealed the exciting news in an adorable Instagram video to his fans.
"My friends at @DisneyPixar have allowed me to make a very exciting announcement... #onward," he wrote in the caption.
Tom will star alongside names like Chris Pratt, Julia Louis-Dreyfus, and Octavia Spencer; with the film hitting cinemas on March 6th, 2020.
Onward is set in a suburban fantasy world, with two teenage elf brothers embarking on an extraordinary quest to discover if there is still a little magic left out there.
“At Pixar we try to create stories that come from some kind of personal truth,” director Dan Scanlon said in a statement. “This film was inspired by my own relationship with my brother.”