Jerwa's comic book career began in 2003, when he submitted a script to Devil's Due Publishing that was accepted, and was eventually published in Frontline #11-14. Soon afterwards, he became the main writer on A Real American Hero and also wrote several G.I. Joe minseries.

On May 18, 2006, Brandon was featured on episode #24 of the Game Show Network's I've Got a Secret; his secret being that in honor of his work on the G.I. Joe comics, Hasbro used his face as the basis for the G.I. Joe action figure Dragonsky.

In 2006 and 2007, Jerwa began writing for Dynamite Entertainment, working on the series Highlander, cowriting the first four issues with Michael Avon Oeming before moving on to a prolific run on Battlestar Galactica.

On Free Comic Book Day 2007, Jerwa met several people affiliated with DC Comics, including Eric S. Trautmann and Greg Rucka. Jerwa and Trautmann struck up a partnership and collaborated on a project called Wide Awake, which appeared first as a short story in Popgun Vol. 2, then as a Free Comic Book Day special, and then later as a free webcomic. In 2009, the duo pitched an idea for a graphic novel to DC's imprint Vertigo, which was accepted, and soon after Jerwa was contacted about working with DC directly.

Jerwa's first work for DC Comics was in September 2009 as the writer of the Inferno co-feature in The Shield, a monthly series that introduced re-imagined versions of the Red Circle Comics superhero characters into the DC Universe.

In late 2009, Jerwa also wrote for a Dynamite series based on Stargate SG-1.