Hadlow's early film appearances were in serious roles, such as in Beyond Reasonable Doubt, but he is perhaps better known in New Zealand for his comedy roles, particularly in the television sitcom Willy Nilly, and some of the voices for the 1989 Peter Jackson puppet film, Meet the Feebles. He also starred alongside New Zealand Maori Comedian, Billy T James in "The Billy T James Show".
In 2009, Hadlow campaigned for the historic Odeon Theatre in Christchurch to be turned into an arts complex for an estimated NZ$60m. The earthquake-prone building was severely damaged in the February 2011 Christchurch earthquake, and later in 2012, the rear of the building was demolished.
In the 2017 Queen's Birthday Honours, Hadlow was appointed an Officer of the New Zealand Order of Merit for services to the arts.
