After graduating from the creative writing program at York University in 1985, Sherman co-founded What Publishing with Kevin Connolly, which produced what, a literary magazine that he edited from 1985 to 1990. Before establishing himself as a dramatist, Sherman's journalistic works such as reviews, essays, and interviews appeared in various publications, including The Globe and Mail, Canadian Theatre Review and Theatrum.
He edited two anthologies for Coach House Press, Canadian Brash (1991) and Solo (1993), and was playwright-in-residence at Tarragon Theatre from 1992 to 1999.
Sherman's first professional productions were A Place Like Pamela (1991) and To Cry is Not So (1991), followed by The League of Nathans (1992, published in book form in 1996), which won a Floyd S. Chalmers Canadian Play Award (1993), and was nominated for the Governor General's Award for English language drama. Among his many other plays is Three in the Back, Two in the Head, which won the Governor General's Literary Award for Drama (1995), and Reading Hebron, which had its most recent production at London's Orange Tree Theatre in March 2011.