Hartinger was born in Washington State. His family moved to Fircrest, Washington when he was an infant. He attended a Catholic (Order of Saint Francis) grade school and middle school, and a Catholic (Jesuit) high school, Bellarmine Preparatory. He earned a bachelor's degree from Gonzaga University in Spokane, Washington, and also studied psychology at Western Washington University.

Hartinger has published seven novels.

His first novel was Geography Club, about teenagers who secretly start a gay-straight alliance at their high school, which was challenged in some American schools, including schools in Hartinger's home town of Tacoma. The novel has two sequels. The Order of the Poison Oak describes the main characters' experiences at summer camp. Split Screen is published as two novels; the reader can turn the book upside down to read the story of a boy trying to choose between two boyfriends ("Attack of the Soul-Sucking Brain Zombies") or the story of an openly bisexual girl who falls for a closeted classmate ("Bride of the Soul-Sucking Brain Zombies"). Hartinger has written a stage version of Geography Club as well as a screenplay for a possible film version of the novel.

Hartinger is the author of fifteen plays that have been performed around the country and that have been included in more than thirty-five playwriting festivals. He has also been recognized for his screenplays, although none of his screenplays has yet been filmed.

He is a sometime-member of the faculty of Vermont College's MFA program. At one time, Hartinger taught creative writing at Tacoma School of the Arts. He has also been a counselor at a youth group home.

Hartinger is also the editor of a fantasy-themed website called TheTorchOnline.com.

Hartinger lives in Seattle with his partner, novelist and AfterElton.com writer Michael Jensen. In 1990, he was a facilitator of Oasis, a support organization for gay teens. He is a co-founder of AS IF! Authors Support Intellectual Freedom, a group of Young Adult authors supporting intellectual freedom. For example, see " GEOGRAPHY CLUB Under Fire Again: My Reponse," by Brent Hartinger, AS IF!, 10 April 2009.