Donovan starred on stage with Amy Ryan in the Los Angeles production of Rabbit Hole. On Broadway, he played Alan Seymour in the 1994 Roundabout Theatre Company revival of Picnic and appeared in Amy’s View with Judi Dench in 1999. Off Broadway, Donovan appeared with Glenn Fitzgerald in the 2001 production of Lobby Hero by Kenneth Lonergan, playing the role of the crooked cop Bill. Donovan has appeared in numerous productions at the Williamstown Theater Festival, including Once in a Lifetime, Under the Blue Sky, and The Glass Menagerie. He has also appeared at the Irish Repertory Theater in New York City. In 2011, he starred with Frances McDormand in the world premiere of David Lindsay-Abaire’s play Good People at the Manhattan Theatre Club.

Donovan was formerly in relationships with Sandra Bullock from 1990 to 1994, and Jennifer Aniston beginning in 1995. Donovan and Aniston ended their relationship after two and a half years in 1998. He later married writer Corinne Kingsbury on a Malibu, California beach in 2005. They divorced in 2008.

Donovan portrayed Joshua, the love interest of Rachel Green, on several episodes of Season 4 of Friends. He also portrayed ‘Cheanie’ in 1997, who was a client of and also dated Ally McBeal in season 1 of the show [1] He later portrayed the priest-son of a large Catholic family in Trinity (1998). He has appeared as a guest star in several television series, such as Magnum, P.I. (1986), The Guardian (2001), Mister Sterling (2003), Exposed (2003), and The O.C. (2003), where he appeared as Jimmy Cooper. From 2007–10, he portrayed Tom Shayes on Damages. In 2005, Donovan began directing episodic television when he directed an episode of The O.C.. In 2007 he guest starred on a season 6 episode of Law & Order: Criminal Intent. In 2009, he directed an episode of the sixth season of Medium. He also directed two episodes of Damages in its third season and an episode of Nip/Tuck in its sixth season. In 2010, Donovan directed the third episode in the sixth season of Weeds, the tenth episode in the fourth season of Gossip Girl, the fourth episode of the fifth season, and one episode of Damages from the third season. In 2011, Donovan directed the Valentine’s Day-themed episode of Glee and the episode “I Kissed a Girl” in the third season. In March 2010, he joined the cast of No Ordinary Family. However, after only one season, the series was cancelled. Donovan guest appeared in the series, Red Oaks.

Donovan’s earliest film roles included Kevin Donaldson in SpaceCamp (1986), a recovering drug addict in Clean and Sober (1988), 1st Lieutenant Luke Sinclair in Memphis Belle (1990) and Paul Matthews in Love Potion No. 9 (1992). Donovan voiced the title character in the Disney animated film Hercules (1997). Donovan played Jesse Zousmer in the Best Picture nominated film Good Night and Good Luck (2005). In 2007, Donovan starred in the film Nancy Drew alongside Emma Roberts. Later, he played Bob Anders, one of the key supporting roles in the Oscar-winning film Argo (2012).

In 2008, Donovan announced his support and campaigned for Barack Obama in the U.S. presidential election of 2008. Donovan supported Obama for re-election in the 2012 presidential election.