Jensen is a native of Seattle, Washington,[1] and a graduate of the School of Visual Arts in New York City.

His graphic novel Green River Killer: A True Detective Story (Dark Horse Comics, 2011) drawn by Jonathan Case, won the Eisner for Best Reality-Based Work and was nominated for a Bram Stoker Award.

[4] He was a story editor on HBO's Emmy-winning limited series Watchmen, receiving Hugo and Nebula nominations for co-writing with Damon Lindelof the episode "A God Walks Into Abar".

His short story work can be found in Captain America: Red White and Blue (Marvel Comics, 2002), Love Is Love: A Comic Book Anthology to Benefit the Survivors of the Orlando Pulse Shooting (IDW Publishing, 2016), Planet of the Apes: When Worlds Collide (Boom!

Better Angels: A Kate Warne Adventure, illustrated by George Schall, was published by Boom!