Smith grew up in Halifax, Nova Scotia. He attended the Halifax Grammar School and Queen Elizabeth High School, and studied French literature at Queen's University, the University of Poitiers, and the University of Paris III. He has an MA in French from Queen's.
As a freelance reporter and cultural commentator, he has published in the New York Review of Books, Details, Toronto Life, Flare, Now, EnRoute and other journals. He won the William Allen White award for magazine writing in 1995.
Smith writes two weekly columns for The Globe and Mail: one in the Review section, on culture and language, and the other in the Style section, an advice column for men.
He was the host of the CBC radio program on language, And Sometimes Y, for two seasons.
Smith was born with complete complex syndactyly, having inherited the deformity from his father and grandfather; Smith's own son, Hugo, was born with the condition.
His early novels, How Insensitive (1994) and Noise (1998), are satirical and comic portrayals of big-city life and the sexual mores of young people. How Insensitive was nominated for the Governor General's Award, at that time the most prestigious Canadian literary prize. Noise was published in German as Glamour by List Verlag. His book of short stories, Young Men, followed in 1999. The opening story in that collection, "Party Going", won the Canadian National Magazine Award for fiction in 1997.
He then published an illustrated fantasy novella, The Princess and the Whiskheads, an allegory about the role of art in a metropolis. The illustrations were by Wesley Bates.
His pornographic novel, Diana: A Diary in the Second Person (2003), was published by Gutter Press under the pseudonym Diane Savage. The novel was republished, under his own name, with a new introduction, by Biblioasis in 2008.
Muriella Pent (2004) is a longer and more ambitious novel, concerning the arrival of a Caribbean writer of mixed race in the stodgy environment of official Canadian culture. It was shortlisted for the Rogers Writers' Trust Fiction Prize, and named as Best Fiction of 2004 by Amazon.ca.
His novel Girl Crazy was published by HarperCollins Canada in 2010.
His new short story collection, Confidence, was published in 2015, and is longlisted for the 2015 Scotiabank Giller Prize.
In 2005 Thomas Dunne Books published Smith's non-fiction book, Men's Style: The Thinking Man's Guide To Dress, which is based on his regular column on men's fashion in the Canadian national newspaper, The Globe and Mail. The book was illustrated by Edwin Fotheringham.
Smith's memoir Blindsided: How Twenty Years of Writing About Booze, Drugs and Sex Ended in the Blink of an Eye is available as an e-book.
Smith is one of the founders of an online men's magazine, DailyXY.