Christa Allen entered show business in 2004 as she was cast as the teenage version of Jennifer Garner in the romantic comedy 13 Going on 30. Two years later, the home-schooled actress landed the TV series called Cake, playing the titular character. Though the show lasted only 13 episodes, Allen lingered on the small screen through guest roles on The Suite Life on Deck, Cory in the House, Grey's Anatomy, ER, CSI, Cold Case and Wizards of Waverly Place, just to name a few.
In 2009, Allen played the younger version of Jennifer Garner yet again. This time it was in the movie Ghost of Girlfriends Past. Two years later, she was cast as one of the main cast members on the ABC drama series Revenge as Charlotte Grayson.