Born in Dublin, Ireland, she moved to the United States as a small child with her mother. Much of her childhood was spent in the small town of Leeds, Alabama, and her early interests included herpetology, paleontology, and fiction writing. As a teenager, she lived in Trussville, Alabama, and, in high school, began doing volunteer work at the Red Mountain Museum in Birmingham, Alabama and spending summers on her first archaeological and paleontological digs. Kiernan attended college at the University of Alabama at Birmingham and the University of Colorado at Boulder, studying geology and vertebrate paleontology, and she held both museum and teaching positions before finally turning to fiction writing in 1992. In 1988, she co-authored a paper describing the new genus and species of mosasaur, Selmasaurus russelli. Her first novel, The Five of Cups, was written between June '92 and early '93, though it wasn't published until 2003. Her first published short story was "Persephone," a dark science-fiction tale, released in 1995. Her most recent scientific publication is a paper on the biostratigraphy of Alabama mosasaurs, published in the Journal of Vertebrate Paleontology (2002).
Kiernan has had short fiction selected for Year's Best Fantasy and Horror series, The Mammoth Book of Best New Horror, and The Year's Best Science Fiction, and her short stories have been collected in several volumes (see Bibliography). To date, her work has been translated into German, Italian, Spanish, Portuguese, Finnish, Czech, Polish, Russian, Korean, and Japanese. In May 1996, Kiernan was approached by Neil Gaiman and editors at DC/Vertigo Comics to begin writing for The Dreaming, a spin-off from Gaiman's very successful title, The Sandman. Kiernan wrote for the title from 1996 until its conclusion in 2001, working closely with Gaiman and focusing not only on preexisting characters (The Corinthian, Cain and Abel, Lucien, Nuala, Morpheus, Thessaly, etc.), but also on new characters (Echo, Maddy, the white dream raven Tethys, etc.). According to an entry in Neil Gaiman's blog, Kiernan was hired to write the novelization for the Beowulf film (scripted by Gaiman and Roger Avary).
Kiernan has often been categorized as a "horror writer," though she has repeatedly and adamantly rejected that categorization. For example, in her blog (2/3/02) she writes: "I'm getting tired of telling people that I'm not a 'horror' writer. I'm getting tired of them not listening, or not believing. Most of them seem suspicious of my motives."
In 2005, she began publishing the monthly Sirenia Digest (otherwise known as MerViSS) consisting of vignettes and short stories : "The MerViSS Project is a continuation of Caitlín’s exploration of the fusion of erotic literature with elements of dark fantasy and science fiction, creating brief, dreamlike fictions." It is currently illustrated by Vince Locke. The digest includes the occasional collaboration with Sonya Taaffe.
Kiernan is a transsexual, a lesbian and Wiccan and lives in Providence, Rhode Island, U.S. with her partner, photographer and doll maker Kathryn A. Pollnac.
Between 1996 and 1997, Kiernan also fronted an Athens, Georgia-based "goth-folk-blues" band," Death's Little Sister, Musical projects named for Neil Gaiman's character, Delirium. She was the band's vocalist and lyricist, and the group enjoyed some success on local college radio and played shows in Athens and Atlanta. Kiernan has said in interviews that she left the band in February 1997 because of her increased responsibilities writing for DC Comics and because her novel Silk had recently sold. She was briefly involved in Crimson Stain Mystery, a studio project, two years later. CSM produced one EP to accompany a special limited edition of Silk, illustrated by Clive Barker (Gauntlet Press, 2000).
