Mariotte was born in Park Forest, Illinois, but he moved at age six because his father, who worked for the United States Department of Defense, was transferred to Paris, France. He graduated from San Jose State University with a degree in Radio/TV/Film.

He is the author of the series Witch Season and has also written many Charmed and Angel books based on the television shows. In 2006 he announced that would retire from the Angel franchise after eleven novels and eleven comics. He also created and writes the Desperadoes series of Weird West-style comic books and Graveslingers.

Recent projects include the one-shot "Presidential Material: Barack Obama," a four-issue adaptation of the film Salvation, as well as Zombie Cop a graphic novel from the Image Comics imprint Shadowline and a novella "The Strip" set in the same fictional universe. and Garrison at Wildstorm.

Besides writing, he owns his own San Diego bookstore, Mysterious Galaxy, along with his partners Maryelizabeth Hart and Terry Gilman.

Buffyverse works

Angel novels

• "Unseen Trilogy"
• "Hollywood Noir"
• "Haunted"
• "Stranger to the Sun"
• "Endangered Species”
• "Sanctuary"
• "Solitary Man”
• "Love and Death”
• "Close to the Ground"

Angel comics

• "The Curse”
• "Old Friends”
• "Doyle Spotlight"

More comprehensive list of novels

• Supernatural: Witch's Canyon published by Harper Entertainment (2007)
• CSI: Brass in Pocket published by Pocket Star (2009)
• Cold Black Hearts published by Jove (2009) (as Jeffrey J. Mariotte)
• River Runs Red published by Jove (2008) (as Jeffrey J. Mariotte)
• CSI: Miami: Right to Die published by Pocket Star (2008)
• 30 Days of Night: Eternal Damnation published by Pocket Star (2008)
• Witch Season 2 published by Barnes & Noble, (2008)
• 30 Days of Night: Immortal Remains published by Pocket Star, (2007)
• Missing White Girl published by Jove, (2007) (as Jeffrey J. Mariotte)
• Las Vegas: Sleight of Hand published by Pocket Star, (2007)
• Age of Conan: Marauders trilogy published by Ace (2006)
• Rumors of the Undead (with Steve Niles), published by Pocket Star, (2006)
• High Stakes Game: Las Vegas Novel 1 published by Pocket Star, (2006)
• Andromeda: The Attitude of Silence published by Tor books, (2005)
• Spring (Witch Season) published by Simon Pulse, (2005)
• Boogeyman published by Pocket Star, (2005)
• Winter (Witch Season) published by Simon Pulse, (2004)
• Fall (Witch Season) published by Simon Pulse, (2004)
• Charmed - Survival of the Fittest published by Simon Spotlight Entertainment, (2004)
• Summer (Witch Season) published by Simon Pulse, (2004)
• Star Trek - The Lost Era ...Deny Thy Father published by Pocket Books, (2003)
• The Slab published by IDW Publishing, (2003)
• Charmed - Mirror Image published by Simon Pulse, (2003)
• Angel - The Casefiles, Volume One (with Nancy Holder and Maryelizabeth Hart)
• Gen13 - Time and Chance (with Scott Ciencin)
• Buffy the Vampire Slayer - The Xander Years, Vol. 2
• Gen13 - Netherwar (with Christopher Golden)

Comics

• Desperadoes:
• A Moment's Sunlight (with John Cassaday, Homage Comics/Wildstorm, 5-issue mini-series, 1997-1998, tpb, 104 pages, July 1998, ISBN 1-58240-013-X)
• "Epidemic!" (with art laid out by John Cassaday and drawn by John Lucas, Homage Comics/Wildstorm, one-shot, 1999, ISBN B0006RRCHQ)
• Quiet of the Grave (with John Severin, Homage Comics/DC Comics, tpb, 128 pages, December 2002, ISBN 1-4012-0018-4)
• Banners of Gold (with Jeremy Haun, 5-issue mini-series, IDW Publishing, tpb, 120 pages, August 2005, hardcover ISBN 1-933239-58-1, softback ISBN 1-932382-96-8)
• Buffalo Dreams (with Alberto Dose, 4-issue mini-series, IDW Publishing, January 2007, tpb, September 2007, ISBN 1600101143)

• Spotlight (with artist Jean Diaz, 5-issue limited series, IDW Publishing)
• Graveslinger (with co-author Shannon Eric Denton and art by John Cboins and Nima Sorat, 4-issue mini-series, Image Comics, October 2007-January 2008, tpb, IDW Publishing, March 2009, ISBN 1600103642)
• "Presidential Material: Barack Obama" (with Tom Morgan, IDW Publishing, 2008)
• Zombie Cop (with Szymon Kudranski, graphic novel, Shadowline, Image Comics, February 2009, ISBN 160706023X)
• Fade to Black (with Daniele Serra, 5-issue limited series, Image Comics, 2010)
• Garrison (with Francesco Francavilla, 6-issue limited series, Wildstorm, 2010)

Short stories

• Tales of Zorro: "Mission Gold"
• Lost Trails: "The Ones he Never Mentioned"
• Full Spectrum: "The Last Rainmaking Song"
• Dead Lands...A Fistful O' Dead Guys: "Behind Enemy Lines"