Cloonan created minicomics and was part of the Meathaus collective before collaborating with Brian Wood on Channel Zero: Jennie One in 2003. Since then, her profile (and workload) has steadily risen; her best-known work to date has been the twelve-issue comics series Demo (2004), also with Wood. Wizard named Demo its 2004 “Indie of the Year.” The series was also nominated for two Eisner Awards in 2005, for Best Limited Series and Best Single Issue (for #7, “One Shot, Don’t Miss”).
Cloonan’s first solo graphic novel, East Coast Rising Volume 1, was released by Tokyopop in 2006. East Coast Rising: Volume 1 marked Cloonan’s third Eisner Award nomination in 2007, this time for Best New Series. She also collaborated with writer Steven T. Seagle on the Vertigo Comics series American Virgin, which was cancelled with the 23rd issue. She is also doing art for the six part upcoming series “True Lives of the Fabulous Killjoys” being co-written by Gerard Way and Shaun Simon.