Milligan is known for playing the role of Ethan Ward in the The CW's 90210, a spin-off of the 1990s prime-time soap opera Beverly Hills, 90210. He was written out of the show at the end of the first season. His film credits include Final Destination 3 (2006), Slither (2006), The Butterfly Effect 2 (2006), In the Land of Women (with Kristen Stewart, Adam Brody and Meg Ryan), (2007), Butterfly on a Wheel (2007), The Messengers (2007) and Extract (2009).
Milligan starred in the short-lived primetime suspense drama Runaway, picked up by the CW network for its inaugural season in September 2006, but canceled in October after only nine episodes. He starred in the Canadian network CTV's made-for-TV movie Eight Days To Live playing O.C. star Rowan's missing son. Milligan has also played minor roles in the television series The Days, Andromeda, The Dead Zone, Alice, I Think, Supernatural and the CBC's Da Vinci's City Hall.
As part of promoting In The Land of Women, Milligan posted a series of eight video diaries on YouTube with the ostensible aim of obtaining a date for the film's premiere.
- Milligan dated Jessica Stroup in 2008-2010
- Milligan auditioned for the role of Twilight's "Edward Cullen" and lost it to Robert Pattinson.