Rachel Hartman was born in Kentucky, but has lived a variety of places including Chicago, Philadelphia, St. Louis, England, and Japan. She has a BA in Comparative Literature, although she insists it should have been a BS because her undergraduate thesis was called "Paradox and Parody in Don Quixote and the Satires of Lucian."

She eschewed graduate school in favor of drawing comic books and in 1996 started publishing the mini-comic Amy Unbounded, which won the 1998 Ignatz Award for Best Minicomic. Publishers Weekly favorably compared it to the writing of Laura Ingalls Wilder and Strange Horizons called it "one of the small treasures of contemporary fantasy." In 2010 Time Techland listed the comic as one of "ten comics that should run forever."

Seraphina, her debut novel, was published on July 10, 2012 by Random House and hit #8 on The New York Times Best Seller list in its first week of publication. Seraphina was awarded the 2013 William C. Morris Award for the best young adult work by a debut author. Foreign language rights to the novel have been sold in sixteen languages, including Spanish and Hebrew. Hartman has announced that Seraphina will be followed by a sequel entitled Shadow Scale in 2013. She lives in Vancouver, BC, with her family and their whippet.