Hart began his first class coaching career for Auckland in 1982. He coached Auckland to the
National Provincial Championship (NPC) title in 1982, 1984 and 1985, and it was during his tenure that, in 1985, Auckland won the
Ranfurly Shield from
Canterbury and began the series of 61 successful defences that remains a record in shield history. Hart, together with
Alex Wyllie, was an assistant coach under
Brian Lochore when the All Blacks won the first
Rugby World Cup in 1987. In 1988, Lochore retired from coaching and Wyllie was appointed to succeed him, an appointment that upset many, especially Auckland, fans. Hart then initially refused to be part of the selection panel but eventually returned as a selector, but was eventually appointed co-coach with Wyllie for the
1991 Rugby World Cup. In hindsight, this was widely regarded to be a mistake: the
personality clash between the two coaches was reflected in a split within the squad into Auckland and Canterbury factions. Following the All Blacks' loss to
Australia in the semi-finals, Wyllie resigned, while Hart sought to become head coach, but was beaten to the post by the then
Otago coach
Laurie Mains. Mains coached the All Blacks to the final of the
1995 Rugby World Cup, which was won by
South Africa, continued as coach for a year-end tour to France, after which he resigned and was replaced by Hart. During Hart's tenure as head coach, the All Blacks achieved their first ever series win in South Africa, in 1996, and won the
Tri-Nations three times, in 1996/97 and 1999. But when New Zealand lost unexpectedly to France in the semi-final of the
1999 Rugby World Cup, Hart, like his immediate predecessors, resigned. As head coach, Hart was in charge of the All Blacks for 41 games, winning 31, drawing one and losing nine. In 1990, Hart was the coach of a New Zealand Under-21 side that toured Australia.
Martin Johnson, who captained England to the title at the
2003 Rugby World Cup, was one of the players in the squad. ==Life after coaching==