Joan Thomas grew up on the Canadian prairies. She studied English at the University of Winnipeg and taught English in three different high schools, as well as in a teacher-training program in the Caribbean. She has worked as a freelance writer, reviewer, and editor, and as Writing and Publishing Consultant for the Manitoba Arts Council.

Thomas has been a frequent book reviewer for the Globe and Mail since 1993 and for two years wrote a biweekly feature review in the Globe. In 2010 she, along with Pasha Malla and Alissa York, selected the stories for the Journey Prize Anthology (McClelland & Stewart) and in 1999 she was co-editor (with Heidi Harms) of Turn of the Story: Canadian Short Fiction on the Eve of the Millennium (House of Anansi Press). Her interview-based features with writers have been published in the Winnipeg Free Press and Prairie Fire.

Thomas has been writing fiction since circa 2000. Her 2008 novel Reading by Lightning won the Commonwealth Prize for Best First Book (Canada and the Caribbean) and the Amazon.ca First Novel Award. Her second novel, Curiosity, was published in April 2010 by McClelland & Stewart. It was named a Quill and Quire Book of the Year and was nominated for the ScotiaBank Giller Prize and the International IMPAC-Dublin Literary Award.