In 1996, Diggs originated the role of the landlord Benny in Jonathan Larson's Tony Award- and Pulitzer Prize-winning Rent, which also starred his future wife, Idina Menzel.

After Rent, he appeared as Mr. Black opposite Menzel's character of Kate in Andrew Lippa's off-Broadway production of The Wild Party at Manhattan Theatre Club.

[13] He also temporarily filled in for Norbert Leo Butz (an original Rent standby) as the love interest Fiyero of Menzel's Elphaba character in Wicked.

The following year, he played a tantric sex god in Doug Liman's Go, and AWOL groom in the coming-of-age drama The Wood alongside Omar Epps.

Malcolm D. Lee's The Best Man features Diggs as the title character, an author and best friend of the groom (portrayed by Morris Chestnut).

Diggs portrayed the title character on the short-lived UPN television series Kevin Hill which despite critical acclaim was not renewed for a second season.

Diggs co-starred as Sam Bennett opposite Kate Walsh in Private Practice, the spin-off of Grey's Anatomy, which ran for six seasons from 2007 until 2013.

[14] Diggs had a guest role on The West Wing as a Secret Service agent in charge of the security detail for the President's daughter.

[15] He also narrated the ESPN Films documentary The Fab Five about University of Michigan basketball players Chris Webber, Juwan Howard, Jalen Rose, Jimmy King, and Ray Jackson.

Diggs has twice appeared on Paramount Network's reality competition series Lip Sync Battle and is the show's only two-time winner.

[24][25] Diggs starred and was executive producer alongside Meagan Good in Terry McMillan Presents: Forever which premiered on Lifetime on August 24, 2024.

[27] Diggs is the co-artistic director of a dance company, Dre.dance, with fellow Broadway veteran and School of the Arts alumnus Andrew Palermo.

[31] From 2021 to 2023, Diggs was in a relationship with Love & Hip Hop: Hollywood star Apryl Jones, who is the mother of singer Omarion's children.