Prior to her role on Undercovers Cox made guest appearances on several television shows. In 2005, she appeard in CSI: NY, and Half & Half, and she appeared in One Tree Hill as faith in season 3 episode 10 the following year. More recently she made a guest appearance on Bones and in four episodes of Paradise Hotel in 2008. She also has a role in the musical I Kissed a Vampire as well as upcoming roles in Crazy, Stupid, Love and After Dark.

Cox was one of only two women selected for the 11-member dance group from a field of over 500 for the This Is It concert series. In Michael Jackson's This Is It, she can be seen dancing with Jackson during the rehearsal of “The Way You Make Me Feel”.

During the 2009 second season of 90210 she appeared in six episodes. She also appears in the fourth episode of season three (October 4, 2010). Her 20-something character, Sasha, becomes the controversial love interest of Tristan Wilds' 17-year-old character, Dixon Wilson. The character is a DJ who met his character at a pizza parlor and a party she DJed on a yacht. Dixon led her to believe he was her age. One of the things that helped them bond despite his status as a high school junior was that they had the same cell phone ringtone. Eventually, Cox's character becomes pregnant.

On October 29, 2009, she was one of the This is It dancers who appeared on The Ellen DeGeneres Show to fulfill host Ellen DeGeneres' birthday wish.

She appeared in all the first season's episodes of Undercovers. She plays a character named Lizzy Gilliam, who is the sister of the female lead and who is unaware of her family's involvement in Central Intelligence Agency activities. Originally, Jessica Parker Kennedy was cast in the role, but Cox replaced her in June 2010 before the first episode of the first season was aired in September 2010. Her character is described as “Boy crazy”.

She is slated to appear in Crazy, Stupid, Love, which is scheduled for April 2011 release.