Kim Mohan was born in Chicago, Illinois, and moved to Williams Bay, Wisconsin when he was five. He became an avid science-fiction and fantasy reader and occasional wargamer, and graduated third in his high school class. He attended Beloit College, switching majors between philosophy, mathematics, and other subjects. “I decided that what I really wanted to do was write, so I sort of fell into a job working for the Lake Geneva Regional News as a reporter, and dropped out of college. That lasted for a few months, then I joined the staff of the Beloit Daily News, where I stayed for nine years." During that time, Mohan worked as everything from a sports writer, an editorial writer, the state editor, and the wire service editor. After nine years, he had grown tired of the newspaper business, and became a freelance writer for various newspapers.

In the summer of 1979, Mohan went to the TSR Periodicals headquarters in Lake Geneva, Wisconsin, and after an interview and some freelance editing assignments as a test, TSR hired him on the spot. He started as part of a three-man staff, and was promoted not too long thereafter to Assistant Editor of Dragon magazine. Mohan was promoted to the Editor-in-Chief position with issue #49 (May 1981). He also performed managerial duties for Strategy & Tactics and Amazing Stories magazine. Mohan also served as the editor and "general handyman" for the original Unearthed Arcana rule book, and he edited Saga of Old City, Gary Gygax’s first novel.

Mohan continued in his position at Dragon magazine until 1986, and again as Editor-in-Chief from 1993 to 1995. He became the editor of Amazing Stories from 1992 through 2001, for which he received Locus Poll Award nominations varying between "Best Editor" or "Best Magazine or Fanzine".

Mohan appears in the 1999 History Channel special In Search of History: The Truth About Science Fiction, which features Harlan Ellison and Larry Niven in a discussion about science fiction literature and movies.

Mohan was the lead editor of the Dungeons & Dragons 3rd Edition design project, until he was promoted to managing editor during the second half of the design stage; Julia Martin took his position from there.

• Planet in Peril (1987, with Pamela O'Neill) (Cyborg Commando trilogy)
• Chase Into Space (1988, with Pamela O'Neill) (Cyborg Commando trilogy)
• The Ultimate Prize (1988, with Pamela O'Neill) (Cyborg Commando trilogy)
• Four from Cormyr: 4 Forgotten Realms Adventures for Characters of Levels 9-12 (Adventure) (1997, with John Terra)

Edited

• Dragon (magazine), 1984—1994
• Amazing Stories, 1991—1995, 1998—2000
• More Amazing Stories, 1998
• Sword and Fist: A Guidebook to Fighters and Monks, 2001, managing editor
• Psionics Handbook, 2001, managing editor