After graduation, Martin toured the states with
John Houseman's
The Acting Company. He appeared in ''Shakespeare's Rock-in-Roles
at the Actors Theatre of Louisville and The Butcher's Daughter'' at the
Cleveland Play House, and returned to
Manhattan to perform in local theatre,
soap operas, and commercials. Finding that auditions, regional theater, and bit parts were no way to support himself, Martin waited tables at several restaurants around the city. He was serving a pizza when his appearance on CBS's
Guiding Light aired in the same eatery. While the show aired, the whole waitstaff gathered around the bar television to cheer his performance. Martin made his Broadway debut in
Timon of Athens, and then performed in
The Government Inspector with
Lainie Kazan. While employed at the
Moondance Diner, he met the playwright
Jonathan Larson, who also worked on the restaurant's staff. In 1996, Larson's musical
Rent took the theatre world by storm, with Martin in the role of gay computer geek/philosophy professor Tom Collins. The 1990s update of
Puccini's
La Bohème earned six
Drama Desk Awards, five
Obie Awards, four
Tony Awards, and the
Pulitzer Prize. In 1998, the West End production of
Rent opened with four of the original cast members, including Martin. He played Tad in the concept album of
Bright Lights, Big City. In 2010, Martin returned to the stage for one of his biggest theater commitments since
Law & Order, performing in the productions of
The Merchant of Venice and ''
The Winter's Tale'' as a part of
The Public Theater's
Shakespeare in the Park at the
Delacorte Theater in Central Park. He played the roles of Gratiano and King Polixenes, respectively. The two shows were performed in repertory, beginning with previews on June 9, 2010, through to the final performance on August 1, 2010.
The Merchant of Venice later transferred to Broadway to the
Broadhurst Theater for a limited engagement, in which Martin reprised his role as Gratiano. The show began previews on October 19, 2010, and officially opened on November 7. The show began a hiatus on January 9 to accommodate
Al Pacino's pre-existing obligations, and resumed from February 1, 2011, to February 20, 2011; Martin did not reprise his role after the hiatus due to other work commitments. He took part in a one-night-only reading benefit of
Romeo and Juliet to celebrate the 50th anniversary of the opening of the Delacorte Theater in Central Park, alongside
Meryl Streep,
Kevin Kline,
Raúl Esparza, and others on June 18, 2012.
Television work Martin landed roles on
Fox's short-lived
413 Hope St. and
Eric Bross's independent film
Restaurant (1998).
Ally McBeals creator,
David E. Kelley, attended
Rents Broadway premiere and remembered Martin when the show needed a new boyfriend for the title character. His performance as Dr. Greg Butters on
Ally McBeal caught the attention of
David Duchovny, who cast Martin as a baseball-playing alien in a 1999 episode of
The X-Files titled "
The Unnatural" that Duchovny wrote and directed. While still shooting
Ally McBeal, Martin heard rumors that actor
Benjamin Bratt planned to leave the cast of
Law & Order. Martin had tried out for the show years before and won the minor role of a car-radio thief named Earl the Hamster, but decided to wait for a bigger part. With the opportunity presenting itself, Martin approached
Law & Order producer
Dick Wolf regarding the opening. Wolf hoped to cast him, and upon hearing that CBS and Fox both offered Martin development deals, he gave the actor the part without an audition. Annual Grand Auction and Flea Market From 1999 to 2008, he starred as Detective
Edward "Ed" Green on
Law & Order. Altogether, he was the fifth-longest serving cast member behind
S. Epatha Merkerson,
Sam Waterston,
Jerry Orbach, and
Steven Hill. He had a brief hiatus at the end of the 2004–2005 season while he was filming the movie adaptation of
Rent in which he reprised the role of Tom Collins. Martin's final episode of
Law & Order aired April 23, 2008, as he was replaced by
Anthony Anderson. Martin returned to NBC a year later as the co-star of
The Philanthropist. On September 14, 2012, NBC announced that Martin would be joining the cast of
Smash during season two for a nine-episode arc as Scott Nichols, the artistic director of the Manhattan Theatre Workshop. Martin also starred in an NBC pilot called
The Secret Lives of Husbands and Wives as Greg Cooke, however it was not picked up to series. Martin played
Joe West in the superhero series
The Flash, a spin-off from
Arrow which premiered in October 2014. In the third season episode "
Duet", Martin played gangster Digsy Foss in Barry and Kara's dreamworld. In its fifth season in 2018, a back injury forced Martin to take medical leave following the season's fourth episode. From the start of the season until then he was almost always leaning against a wall or sitting down. Martin returned from medical leave in January 2019 with the season's fifteenth episode. He departed as a series regular after the eighth season, having been cast in the NBC pilot
The Irrational, in which he already stared.
Film work On March 4, 2013, it was announced that Martin would replace
Lenny Kravitz as
Marvin Gaye in
Sexual Healing, an upcoming biopic directed by
Julien Temple, and produced by Vassal Benton and Fred Bestall. Martin had been attached to the Marvin Gaye biopic for years and had stated that it was his dream role to portray the legendary Motown singer. (crew members were said to have not been paid fully for their work on the film). Approximately 70% of the film had been shot. He co-produced the off-Broadway production of
Fully Committed with
Rent co-star
Adam Pascal (and two other producers). == Personal life ==