[5] On the advice of Prime Minister David Lange, Queen Elizabeth II appointed Reeves the 15th Governor-General of New Zealand effective from 20 November 1985.

His appointment was met with some scepticism due to his previous political involvement in Citizens for Rowling, opposing the 1981 Springbok Tour, and the fact that he was an Anglican bishop.

Leader of the Opposition Jim McLay opposed the appointment on these grounds,[6] asking "How can an ordained priest fulfil that [constitutional] role?"

Many Māori groups welcomed the appointment, with Sir James Henare arguing that "It must be a fruit of the Treaty of Waitangi to see a person from our people.

He hosted the first open day at Government House on 7 October 1990, and employed the first public affairs officer, Cindy Beavis, to promote the governor-general's role.

In November 1987 Reeves made comments critical of Rogernomics, stating that the reforms were creating "an increasingly stratified society".

"[8] On a state visit to Vanuatu in 1988, Reeves was invited to kill a pig at a ceremony, creating controversy as he was patron of the Royal New Zealand Society for the Prevention of Cruelty to Animals.

This was followed by a similar incident when Reeves was a member of a party that shot an endangered bird during a trip to New Zealand's sub-Antarctic islands in December 1989.

The bird was a light-mantled albatross and protected under the Wildlife Act 1953, however the Department of Conservation Southland operations manager Lou Sanson accepted that the shooting was accidental.

He was also Deputy Leader of the Commonwealth Observer group to South Africa, Chair of the Nelson Mandela Foundation, and Visiting Montague Burton Professor of International Relations at the University of Edinburgh.

On 12 December 2007 it was reported that Reeves was involved with "secret talks" to resolve Fiji's year-long political crisis, following the 2006 Fijian coup d'état.

[21] The University of Oxford conferred on him the degree of Doctor of Civil Law in 1985 and his college, St Peter's, appointed him an Honorary Fellow in 1981 and a Trustee in 1994.