Atkinson was born in Little Rock, Arkansas. She moved to New York at age 17 and attended Barnard College. After a year, she returned to Arkansas and graduated from Hendrix College in 2001 with a degree in political science and religion.

Since 2003, Atkinson has skated and announced as a member of the Gotham Girls roller derby team under the name of 'Margaret Thrasher'.

She was seen by Director Jace Alexander when she performed in a Neighborhood Playhouse school showcase, which led to her appearances in Law & Order and Rescue Me. While on hiatus between the 2004 and 2005 seasons of Rescue Me, she starred as Helen, the sweet-faced, plus-size librarian in Neil LaBute's 2004 play Fat Pig, for which she won a Theatre World Award for 'Outstanding Off-Broadway Debut', as well as receiving nominations for both a Lucille Lortel Award and an Outer Critics Circle Award. She also appeared in a Broadway revival of The Ritz in 2007. Atkinson's film and television credits include Inside Man, Margot at the Wedding, Another Gay Movie, Law & Order and Rescue Me.

In 2006 Atkinson became the face of a fictional character called Chunky Pam. Pam was featured in a Christmas promotion for MTV called XXXLMAS, a Valentine's Day promotion called Pampered, and a one-off music video titled Dirrrty Jerzy, in which she raps about being from New Jersey.

Atkinson stars as 'Dakota Prentiss' in a 14-episode noir science fiction thriller podcast called Steal the Stars (2017), the story of two government employees guarding the biggest secret in the world: a crashed UFO.