In 2010, Ellis co-starred opposite Wesley Snipes in the action film Game of Death. She played the leading role in the independent film The Tested based on the award-winning 2005 short film of the same name. In 2011, she appeared in the critically acclaimed period drama The Help directed by Tate Taylor, as Eula Mae Davis, one of the maids, for which she received awards as a part of the ensemble cast. In 2014, she played Vicki Anderson in the biographical drama film Get on Up about the life of singer James Brown, also directed by Tate Taylor. As lead actress, Ellis starred in the independent films Money Matters (2011), The Volunteer (2013), Romeo and Juliet in Harlem (2014), and Una Vida: A Fable of Music and the Mind (2014). She also played the leading role in the 2012 television film Abducted: The Carlina White Story.
From 2010 to 2013, Ellis had a recurring role in the CBS series The Mentalist, as Madeleine Hightower. She also played Ashley Judd's best friend in the 2012 ABC miniseries Missing, and had another role on the CBS procedural, NCIS: Los Angeles. Ellis also starred as one of the lead characters in the 2013 AMC pilot The Divide. When WE tv picked up the show, Ellis left and was recast with Nia Long.