In 1997, Egan made her first appearance in a Disney film as the feisty Megara from Disney's Hercules. This brought her critical acclaim and recognition for her voice acting skills. She later reprised the role in most of the character's subsequent appearances including the episode "Hercules and the Aetolian Amphora" from the television series, House of Mouse, and Kingdom Hearts II.
She also voiced Madame Gina in Porco Rosso and Lin in Spirited Away and played Heather Bartlett in Gotta Kick It Up!.
Apart from acting, Egan has a frequent career in music. She recorded "I Won't Say (I'm in Love)" during her role as Megara for the Hercules soundtrack, and garnered critical acclaim for her singing for her role as Belle on Broadway.
Later, she provided the singing voice of Angel in Lady and the Tramp II: Scamp's Adventure, in which she recorded "Always There" alongside Roger Bart, Jeff Bennett, and returning Disney icon Jodi Benson.