Sinclair, one of New Zealand's most successful playwrights and screenwriters, has had a long screenwriting partnership with Academy Award nominees Peter Jackson and Frances Walsh (Heavenly Creatures, The Frighteners), most recently including The Lord of the Rings: The Two Towers. In 1990, he co-scripted the feature film Meet the Feebles, and in 1991, Braindead (aka Dead Alive), which subsequently won Best Screenplay at the 1993 New Zealand Film and Television Awards.

In April of 2002, Sinclair directed his short film The Bach, a twelve-minute comedy thriller set in the Coromandel.

For the stage, Sinclair co-wrote (with Danny Mulheron) "The Sex Fiend," which premiered at Bats Theatre in 1989, went on to play return seasons in all the main centers, and continues to be performed by repertory companies around the country. It has also been produced in Australia, most recently in December of last year. "Ladies Night" (co-written with Anthony McCarten) has enjoyed international success with recent productions in Australia, Great Britain, Germany, France, Switzerland, Scandinavia, Finland, Austria, Argentina, Uruguay, Chile, Brazil, Puerto Rico and Canada. Last year in France it won the Moliere Award for the Best Stage Comedy for 2001 and it has currently become a hit in Moscow.

Sinclair began his career as writer and director for the Maori and Pacific Island Theatre Group, Taotahi, which he co-founded. His several years with the group culminated with the production of "Le Matau," the first play to deal with the Pacific Island experience in New Zealand.

Other plays include "Caramel Cream," "Blowing It" (co-written with Stephen Papps), and the musicals "Big Bickies" and "Braindead." In June of 2002 his historical drama "The Bellbird" was produced as a main bill for the Auckland Theatre Company. Peter Calder of the NZ Listener called it "a play of heart and soul and a valuable addition to our literature."

Sinclair's one-hour television comedy Love Mussel, starring the late Kevin Smith, screened in July of last year. The NZ Listener cited it as the best one- hour television comedy-drama for 2001.

His first novel, the children's book, Thief of Colours, was published by Penguin Books in 1995. His first adult novel, entitled Dread, published in July 2000, was described in the review in the New Zealand Listener as "an impressive debut." His collection of poetry, The Dwarf and the Stripper, will be published early in 2003.

A recent article in the Auckland Metro referred to Sinclair as "New Zealand's finest comic writer."