He often collaborates with fellow director Ron Clements and is best known for writing and directing the Disney animated films The Great Mouse Detective (1986), The Little Mermaid (1989), Aladdin (1992), Hercules (1997), Treasure Planet (2002), The Princess and the Frog (2009), and Moana (2016).

Due to a shortened production schedule and multiple story rewrites, Roy E. Disney assigned Mattinson to serve as director/producer while Ron Clements was brought in as another director.

[6] While working on The Great Mouse Detective, newly appointed Disney CEO and chairman Michael Eisner and Jeffrey Katzenberg issued invitations to the animation staff for their first held "gong show" session.

[7][8] With The Little Mermaid in production in 1986, Musker joined Clements in expanding the original treatment into a twenty-page rough script, eliminating the role of the mermaid's grandmother and expanding the roles of the Merman King and the sea witch,[9] and were later joined by Off-Broadway musical composers Howard Ashman and Alan Menken who collaborated on the song and musical score.

[13] With Treasure Planet completed in 2002, Clements and Musker later inherited Fraidy Cat, which was originally a project developed by Dutch animation director Piet Kroon.

[19] Fraidy Cat, however, never saw its light of day, as David Stainton, then-president of Walt Disney Feature Animation, refused to green-light the project.

[24] After directing The Princess and the Frog, Clements and Musker started working on an adaptation of Terry Pratchett's Mort,[25] but obtaining the film rights prevented them from continuing with the project.

In July 2013, it was revealed that the film, titled Moana, would be "a Polynesian tale involving the island folk and the idols made famous the world over".