Eric Millegan was born in Hackettstown, New Jersey. He grew up in Springfield, Oregon. He studied acting at the Interlochen Arts Camp at Interlochen Center for the Arts in Michigan, before studying musical theater at the University of Michigan. He currently lives in New York City. In 2003, Out named him the "Hottest Up-and-Coming Openly Gay Actor" of the year. Many of Millegan's credits are in musical theater.
He began his musical theater career at age 7, in the 1981 Eugene Opera production of Menotti’s Amahl and the Night Visitors. He continued with the company in several other productions, including Madame Butterfly, La Bohème, Carmen, and Hansel and Gretel. Millegan appeared on Broadway in the 2000 production of Jesus Christ Superstar. In January 2005, he starred as Harold opposite Estelle Parsons' Maude in the world premiere of Tom Jones and Joseph Thalken's Harold & Maude: The Musical at the Paper Mill Playhouse in Millburn, New Jersey. In 2006, he returned to Eugene, Oregon to play Frederic in Eugene Opera's production of The Pirates of Penzance.
In August 2009, Millegan released a video on YouTube in which he came out about his experiences living with rapid-cycling bipolar disorder.
- 100 Centre Street (2001) - Michael Truskie
- Law & Order: Criminal Intent (2002) - Eddie Dutton
- Curb Your Enthusiasm (2004) - delivery person
- Bones (2005-2008, 2010, 2016) - Zack Addy
- Soda Pop (2001) - Jamie
- On Line (2002) - Ed Simone
- The Phobic (2006) - Reed Jenkins