Thoms was born and raised in Baltimore, Maryland, the daughter of Mariana and Donald Thoms. She has a brother, Austin. She started studying acting when she was ten and later on attended the Baltimore School for the Arts. She now holds a BFA from Howard University and a postgraduate diploma in acting from the Juilliard School (Group 30), where she was a classmate of actors Lee Pace and Anthony Mackie. She is currently playing the role of Joanne in the musical RENT on Broadway.
Thoms is known for her role of Mahandra McGinty in the television show Wonderfalls. She also played the part of Sasha in the series "As If", which was cancelled after three episodes. Most recently she has been added to the cast of the CBS crime drama Cold Case, as the narcotics detective, Kat Miller. Thoms has also made guest appearances on Law & Order and The Shield.
Thoms has appeared in several movies, most notably in the film adaptation of the Broadway musical Rent in which she plays Joanne Jefferson, lawyer and lover of Maureen Johnson (Idina Menzel). She took over the role from Fredi Walker, who played Joanne in the original Rent Broadway show and who decided not to reprise her role due to her age. Prior to being cast as Joanne, she had been a big RENThead herself and had seen it in Broadway several times. She had also been auditioning for the theatre production for years but had never gotten the part. On July 18, 2008, she announced on her Myspace she will be joining the final cast of RENT starting July 26, 2008, playing the character Joanne, replacing Merle Dandridge.
She was featured in the 2002 Comedy Central film Porn 'n Chicken and the 2004 films Brother to Brother and The Warrior Class. Thoms appeared in the 2006 release of the film version of The Devil Wears Prada as Lily. Thoms has completed filming on the City Lights Pictures movie Descent along with Rent co-stars Wilson Jermaine Heredia and Rosario Dawson and will soon begin filming Jimmie with co-stars Vanessa Williams and Brian McKnight. Recently, she appeared in Quentin Tarantino's Death Proof, again, alongside Rosario Dawson.
Thoms made her Broadway debut in Regina Taylor's Drowning Crow. She has also appeared in several off-Broadway and regional productions, including Up Against the Wind (New York Theater Workshop), The Oedipus Plays (The Shakespeare Theater), A Raisin in the Sun (Baltimore CenterStage) Joe Turner's Come and Gone (Missouri Rep), The Exonerated (Off Broadway's The Culture Project) and The Antigone Project (The Women's Project).