Jacobs' first acting role came as Adele Congreve on the television series The Book of Daniel. Although she played Kim in the pilot of Traveler, the role was given to Pascale Hutton when ABC acquired the series. Jacobs subsequently made guest appearances on Fringe and Law & Order: Criminal Intent. In 2006, she starred in an Off-Off-Broadway production of Chris Denham's cagelove. While overall critical reaction to the play was negative, Jacobs earned praise in several reviews.The New York Times advised readers to "remember the name of Gillian Jacobs, a stunning Juilliard graduate who has the glow of a star in the making".
Jacobs has appeared in theatrical productions such as The Fabulous Life of a Size Zero (2007), A Feminine Ending (2007), and The Little Flower of East Orange (2008). Her film work includes Blackbird (2007), Choke (2008), Gardens of the Night (2008), and The Box (2009). In March 2009, Jacobs joined the cast of the NBC sitcom Community as Britta Perry, a high school dropout who aspires to become a psychologist.Community was canceled by NBC on May 9, 2014, and later that month, it was reported that Jacobs had landed a recurring role as Mimi-Rose Howard in the upcoming fourth season of the HBO series Girls. In June 2014, Yahoo! Screen picked up Community for a sixth season.
^"A New Generation". Purple. My Fashion Database. Spring–Summer 2009. Retrieved July 22, 2012. "What's your full name? - Gillian Maclaren Jacobs ... What are your parents' names? - Martina Magenau Jacobs and William F Jacobs Jr"