The ninth child in a family of 13 girls, Jennifer Fallon was born in a suburb of Melbourne, Australia. After living in various areas of Australia, including Canberra, Darwin, and a remote mining settlement, Fallon settled in the Northern Territory in 1980. She has two daughters and a son. She has had 32 foster children and friends refer to her home as "the ashram" due to the large number of stray teenagers that still inhabit her house at irregular intervals.

Fallon has worked as a youth worker, a store detective, shop assistant, an advertising sales rep and executive secretary, among other things. She has managed two hire car companies, an ISP, and a video shop, as well as founding the Anzac Hill Gymnastics Club in 1991. She is a member of the Business & Professional Women's Association and is often in demand as a guest speaker.

Fallon started writing when she was about 14. Her mother, who died when Fallon was 13, was an aspiring children's writer who encouraged her daughter to write. She started writing fantasy in 1990 when she decided she would be better off writing something for herself, rather than trying to please everyone else. In 1995, Jennifer vowed to either get published by the year 2000 or give up writing and get a real job. Her first novel,Medalon, was released in Australia in August 2000 and hit the bestseller list the first week it was released, as well as being shortlisted for the 2000 Aurealis Awards as the best Fantasy novel.