Union is known for her performances in the romantic comedy films "The Brothers" (2001), "Deliver Us from Eva" (2003), "Daddy's Little Girls" (2007), "Think Like a Man" (2012) and "Think Like a Man Too" (2014). She also had starring roles in the CBS medical drama series "City of Angels" (2000) and films "Bad Boys II" (2003), "Cradle 2 the Grave" (2003), "Neo Ned" (2005), "Cadillac Records" (2008), "Top Five" (2014) and "Breaking In" (2018). In 2013, Union began starring as lead character in the BET drama series "Being Mary Jane", for which she has received an NAACP Image Award. She co-starred in the 2016 film "The Birth of a Nation", and next appeared in "Almost Christmas" (2016) and "Sleepless" (2017).