Nick Mamatas was born on Long Island, New York and attended the State University of New York at Stony Brook, New School University, and Western Connecticut State University. He currently lives in California, in the Bay Area.

Mamatas funded his early writing career by producing term papers for college students.

Mamatas' work has appeared in Razor Magazine, The Village Voice, and various Disinformation Books and BenBella Books' Smart Pop Books anthologies.

His short novel Northern Gothic (Soft Skull, 2001) was nominated for the Bram Stoker Award for Best Long Fiction in 2002. In 2007, a signed/limited hardcover edition, illustrated and with a slipcase, was published in German by Edition Phantasia.

His first full-length novel, Move Under Ground (Night Shade Books, 2004/Prime Books, 2006), combined the Beat style of Jack Kerouac with the cosmic horror of H. P. Lovecraft's Cthulhu Mythos. This novel was nominated for both the Bram Stoker Award for Best First Novel and the International Horror Guild Award for Best First Novel in 2005, and made the Locus Magazine Recommended Reading List for books published in 2004.

In 2006, Move Under Ground was one of the first books to be published in paperback by the German publisher Edition Phantasia. In early 2007 he decided to distribute it online for free under a Creative Commons license.

His most recent novel Under My Roof (Soft Skull, 2007) has been published in both Germany and Italy in addition to its American publication. The German edition was nominated for the Kurd-Laßwitz-Preis for science fiction originally published in a foreign language. It came in last place in the voting.

In August 2006, Mamatas was named co-fiction editor of Clarkesworld Magazine. In August 2008, Mamatas left Clarkesworld and began working for Viz Media to edit the firm's forthcoming line of Japanese science fiction, fantasy, and horror in translation. Clarkesworld's 2008 issues earned it a nomination for the Hugo Award for Best Semiprozine. Mamatas, along with editor Sean Wallace and publisher Neil Clarke, were named as the magazine's principals. Mamatas, along with Clarke and Wallace, were nominated for the World Fantasy award for Clarkesworld in the nonprofessional special award category, also for the 2008 issues.

Mamatas edited the posthumous collection of short fiction, Queen of the Country, by dark fantasist dgk goldberg in 2008.

A collection of short fiction, You Might Sleep..., including a new novella, was published in March 2009.

"The Dude Who Collected Lovecraft," written by Mamatas and Tim Pratt, was nominated for the Stoker award for achievement in Short Fiction in March 2009.

Mamatas is co-editing the original horror anthology Haunted Legends with Ellen Datlow forthcoming in 2010.

Mamatas is most known for his horror and dark fiction, but claims broad influences. Writer Laird Barron described the short fictions in You Might Sleep... as running "the gamut of science fiction, fantasy, metafiction, horror, generic lit, to the realms of the effectively unclassifiable."

A number of his short works, such as the novelette "Real People Slash" and the flash fiction "And Then And Then And Then", explicitly combine Lovecraftian themes with the autobiographical motifs and trangressive prose style of New York's "downtown" literary scene of the 1970s and 1980s. The short story "That of Which We Speak When We Speak of the Unspeakable", first published in the anthology Lovecraft Unbound is a pastiche of Lovecraft and several of the works of Raymond Carver.

Novels

• Northern Gothic (2001)
• Move Under Ground (2004)
• Under My Roof (2007)

Short story collections

• Stories And Essays (2003)

• You Might Sleep... (2009)

Anthologies

• The Urban Bizarre (2004)
• Spicy Slipstream Stories (with Jay Lake) (2008, forthcoming)
• Haunted Legends (with Ellen Datlow) (2010), forthcoming)

Non-Fiction

• Kwangju Diary (1999)

Poetry

• Cthulhu Senryu (2006)

Editor

• Phantom #0 (November 2005)
• Clarkesworld Magazine (August 2006-August 2008)
• Viz Media (August 2008—present)