Dibdin was the son of a physicist, and was brought up from the age of seven in Lisburn, Northern Ireland where he attended Friends' School. He graduated with a degree in English from Sussex University, and then went to study for a Master's degree at the University of Alberta in Edmonton, Canada. After publishing his first novel, a Sherlock Holmes pastiche, he lived for four years in Italy, teaching at the university in Perugia. Latterly he lived in Seattle, Washington.
Dibdin was married three times, most recently to the novelist K. K. Beck. His death in 2007 followed a short illness.
Dibdin is best known for his Aurelio Zen mysteries, set in Italy. The first of these, Ratking, won the 'Gold Dagger' award of 1988. This series of detective novels provide a penetrating insight into the less visible aspects of Italian society over the last twenty years. The earlier books have a lightness of touch that gradually becomes much darker. The character of Zen himself is anti-heroic, which adds much to the books' irony and black humour. A final Zen book, 'End Games', appeared posthumously in July 2007.
He also wrote other detective works set in America and in England.