After performing with the Los Angeles Junior Philharmonic in high school and studying music and art at Cal State, Northridge, Hahn started a career as an orchestral percussionist before segueing to animation. He joined the Disney Studio in 1976, earning his first credit as a production assistant on "Pete's Dragon" (1977). The next phase of his education was supervised by an acknowledged master of animation. Hahn served as an assistant animator to Wolfgang "Woolie" Reitherman--one of the legendary "Nine Old Men" from the glory days of the studio in the 30s and 40s--on the 1981 feature "The Fox and the Hound". He subsequently gained production credits on the failed cartoon epic "The Black Cauldron" (1985) and the more modest but charming "The Great Mouse Detective" (1986).
Moving to England on an assignment in the mid-80s served to transform Hahn's career. He signed on as associate producer on Disney and Amblin Entertainment's ambitious live- action/animation hybrid "Who Framed Roger Rabbit" (1988). The film's huge success paved the way for Hahn's first outing as a producer, "Beauty and the Beast". A successful formula had been established with Disney's prior animated outing "The Little Mermaid" (1989)--an isolated innocent protagonist with magical little friends learns important life lessons to the accompaniment of Broadway-styled show tunes--but Hahn and directors Gary Trousdale and Kirk Wise fine-tuned it, created a classic for the entire family and single-handedly revived the musical as a commercial film genre. In fact, the film generated a hit Broadway musical. As for Hahn's follow-up, in addition to setting box-office records, "The Lion King" took Disney marketing and merchandising to new heights.
Hahn reteamed with the "Beauty and the Beast" helmers for an ambitious musical adaptation of "The Hunchback of Notre Dame" (1996), a kinder, gentler take on Victor Hugo's 1831 novel. Nonetheless, while widely acclaimed, the film took some heat for its harsh subject matter and frightening situations. That same year, Hahn extended his commitment to Walt Disney Feature Animation for several more projects over the subsequent seven years including "Atlantis: The Lost Empire" (2001), an animated feature with Trousdale and Wise.