The UK will piggyback on New Zealand's diplomatic missions in Tonga and Vanuatu with the launch of new High Commissions this year.
In October, the UK said it would expand its presence in the Pacific, with diplomatic posts in Samoa, Tonga and Vanuatu.
On Tuesday, the Foreign and Commonwealth Office said it would co-locate and work with New Zealand in Nuku'alofa and Port Vila.
The announcement comes during a visit to the UK by New Zealand Prime Minister Jacinda Ardern.
Each new High Commission is expected to have around five or six staff who will focus on strengthening engagement with the Pacific.