He also starred as narcotics crime lord Richard Wheatley on the Law & Order: Special Victims Unit spinoff Law & Order: Organized Crime; Lt. Carter Shaw on the TNT series Dark Blue; in two short-lived CBS dramas, Hostages and Stalker; and in the 1994 remake of the film Miracle on 34th Street.

[4] As a teenager, he began taking trips to visit his biological father, who owned the West Fourth Street Saloon in Greenwich Village, New York.

V, with whom McDermott has remained close, encouraged him to pursue an acting career,[6] and began writing roles for him into her plays.

[8] He then graduated from Jesuit-run Fordham University with a BA in 1983,[12] as well as studying under Sanford Meisner at the Neighborhood Playhouse School of the Theatre in New York City.

[13] McDermott made his screen debut in Hamburger Hill in 1987 before starring in the 1989 film Steel Magnolias opposite Julia Roberts as her husband Jackson Latcherie.

[17] In 1994, McDermott starred in Miracle on 34th Street as Lawyer Bryan Bedford, which has grossed $46.3 million dollars in the worldwide box office.

Executive producer David E. Kelley cited "economic and creative realities" as a result of pressure from ABC to reduce costs.

[18] In 2004, McDermott starred alongside Julianna Margulies four-part mini-series The Grid, playing FBI Special Agent Max Canary in an anti-terrorist unit.

On October 30, 2008, TV Guide reported that McDermott was due to co-star alongside Shannen Doherty in the film Burning Palms, a satire based on Los Angeles stereotypes told through five intertwining storylines.

[21] Beginning in 2009, McDermott starred in the TNT drama Dark Blue, playing a veteran cop who heads a squad of undercover LAPD officers.

In 2011, McDermott starred on American Horror Story on FX as Ben Harmon, a psychologist and cheating husband.

He returned to the second season as a new character due to the series' anthology format, this time portraying Johnny Morgan.

[26] He appeared in the action thriller Olympus Has Fallen as a treacherous Secret Service Agent who helps a group of terrorists seize control of the White House.

[28] In 2014, McDermott began starring on another short-lived CBS television series Stalker in one of the lead roles, portraying Detective Jack Larsen opposite Maggie Q.