St. Andre was born in Ogden, Utah. He lives in Phoenix, Arizona, U.S.. On August 27, 2010, he retired after thirty-six years of service to the city of Phoenix as a public librarian.

St. Andre is the original designer of the 'pen-and-paper' role-playing game Tunnels & Trolls which was first released by Flying Buffalo, Inc. in 1975. In addition to writing the game rules, Ken was one of the creators of solitaire adventures which allowed players to experience the game without a game master or judge.

St. Andre has written many modules and stand alone adventures for Tunnels and Trolls. Some of his titles include:

• The Deathtrap Equalizer Dungeon
• Naked Doom
• Arena of Khazan
• Goblin Lake
• The Lair of the Silver Serpent
• The Toughest Dungeon in the World
• Agent of Death
• Strange Destinies
• Hot Pursuit

He also worked as a designer on the role-playing games Stormbringer and Monsters! Monsters!, and the computer game Wasteland. In 2008 he modified the 7th edition Tunnels and Trolls to bring the game world into modern times and turned it into a superhero rpg called Power Trip.

In 1986 Ken was also the first editor for a fan club newsletter based around the Adventure Construction Set computer game, one of the rare cases of a professional designer leading gamer activities for another designer's game.

He has written various short stories and novels.

• "Old Soldiers Never" (1989), in Shrapnel: Fragments from the Inner Sphere, a Battletech anthology.
• "Turtle in the Tower" (1990), in Shadowrun: Into the Shadows edited by Jordan K. Weisman. An anthology of stories based on the Shadowrun role-playing game. (ISBN 1-55560-118-9).
• "The Two Worst Thieves in Khazan" (1992) in "Mages Blood and Old Bones".
• "The Triple Death" (1995), in Enchanted Forests edited by Katharine Kerr and Martin H. Greenberg. An anthology of stories about magical woods. (ISBN 0-88677-672-4).
• "Moral Invaders" (2005) in Flash Fantastic. A very short story in issue 16 of the online magazine.
• "A Thief's Day in Khazan" (2005) in Golden Heroes.
• Dragon Child (2006), by Ken St. Andre and James L. Shipman. A fantasy novel based on the Tunnels & Trolls role-playing game.
• Griffin Feathers (2008), by Ken St. Andre. A collection of linked short stories based on the Tunnels & Trolls role-playing game.
• "Introduction: Trollgod's Treasure Hunt" (2008) in Troll Tunnels, edited by Christina Lea. A collection of short sword and sorcery tales.
• "The Awakening" (2008) in Troll Tunnels, by Ken St. Andre and James L. Shipman.

Ken St. Andre has a wife, Cathy, and two grown children, a daughter named Jillian and son named James.