Mary Kirchoff was born and raised in Lake Geneva, Wisconsin, the city where the Dungeons & Dragons role-playing game was invented. "I went to school with Ernie Gygax and a number of people who later worked for TSR... I was vaguely aware of the people who played things like the D&D game at school. Then I went away to college and learned more about roleplaying games. I realized [they] were coming from my home town." Kirchoff graduated from Lawrence University with a B.A. in English. She was hired by TSR to be editor of the Polyhedron newszine in 1982, shortly after its second issue. Kirchoff also did graphic design for Dragon magazine, and worked with Roger Moore on TSR's Ares science-fiction magazine.

Kirchoff's first book was Light on Quests Mountain, for TSR's Endless Quest series, and she wrote several other books in the collection. Kirchoff decided to write full time, supposted by her then-boyfriend. TSR game editor and designer Steve Winter. In September 1985, Kirchoff married Steve Winter. She began writing freelance for TSR again, working on book such as The Art of the Dragonlance Saga and Leaves from the Inn of the Last Home, and later rejoined the company as a full-time editor. Meanwhile, Kirchoff began looking for a new Forgotten Realms book to follow Darkwalker on Moonshae: "I went to the slush pile and read the first 30 pages of a book called Echoes of the Third Magic by a guy named Bob Salvatore. The story didn't really fit what we were looking for, but there was something about the writing that grabbed me."

Kirchoff wrote six novels for the Dragonlance setting, including Wanderlust, Flint the King, Kendermore, and the Defenders of Magic trilogy. She also co-created the Dark Sun setting with Troy Denning and Tim Brown. She was eventually promoted to head of the Book department: "Every book we published hit numerous bestseller lists -- it was a golden time." After five years of writing Dragonlance novels at night and running the Book department by day, she withdrew to spend more time with her children; five years later, she returned as Executive Editor of the restructured book-publishing program.

Her works are translated into more than nine languages..

She is an acquiring editor for TOR Books. She is also a Certified Integrative and Blueprint personal coach. She was formerly Chief Marketing Officer at 38 Studios. Until December 2004,she was Vice President of Marketing, Publishing, and Tabletop games over the Dungeons & Dragons and Avalon Hill brands at Wizards of the Coast .