Aaron's career in comics began in 2001 when he won a Marvel Comics talent search contest with an eight-page Wolverine back-up story script. The story, which was published in Wolverine #175 (June 2002), gave him the opportunity to pitch subsequent ideas to editors. In 2006, Aaron made a blind submission to DC/Vertigo, who published his first major work, the Vietnam War story The Other Side, which was nominated for an Eisner Award for Best Miniseries, and which Aaron regards as the "second time" he broke into the industry. Following this, Vertigo asked him to pitch other ideas, which led to the series Scalped, a creator-owned series set on the fictional Prairie Rose Indian Reservation and published by DC/Vertigo.