Graeme Simsion was born in Auckland, New Zealand in 1956. As an undergraduate, he attended university in Australia and studied physics. Simsion was interested in pursuing research in theoretical physics, but he also showed a strong aptitude for database design and decided to pursue a career in information technology. After graduating with his bachelor's degree, Simsion worked as a computer operator and built a successful career in the IT world. In 1982, he started his own IT consulting business. Simsion also continued to pursue further education, and he completed a Ph.D. in data modeling at the University of Melbourne in 2006.
In about 2006, at the age of fifty, Simsion became intrigued with the idea of writing film scripts. He enrolled in a screenwriting class and wrote the first version of The Rosie Project as a screenplay. Between 2006 and 2012, Simsion also went on to write a number of other scripts and produce films based on those scripts. He eventually came to feel that The Rosie Project would work better as a novel and adapted the script into a book manuscript. The manuscript attracted attention in both Australia and elsewhere, and it was published in 2013.
Subsequent to the publication of his first novel, Simsion has developed a successful literary career including the two Rosie sequels, two other novels, and a number of short stories. In addition to writing, Simsion continues to be active in the film and IT industries.
Simsion is married to Anne Buist, a researcher and psychiatrist who is also a published fiction author. Simsion and Buist co-authored a novel, Two Steps Forward, which was published in 2017. Simsion and Buist also have two children together.