"[Meghan and Harry] wanted to hit the ground running after their marriage to focus on their charitable interests and Meghan is really looking forward to representing Her Majesty on her first major Commonwealth tour to Australia, Fiji, Tonga and New Zealand", the source said.
In the case of Fiji and Tonga, they were invited to spend time there by the Foreign and Commonwealth Office.
They will then head to Wellington, Abel Tasman National Park, Auckland and Rotorua in New Zealand.
"The programme across these four Commonwealth countries will focus on youth leadership, environmental and conservation efforts, including the dedication of several new Queen's Commonwealth Canopy projects, and the recovery and rehabilitation of servicemen and women through the Invictus Games Sydney 2018".
"Meeting Prince Harry and Meghan is something the team will never forget, but we were all so honoured to have been in such incredible company of other healthcare professionals, children, families and volunteers".
There had always been speculation that the pair would visit New Zealand.
The pair have confirmed they'll be in the country from Tuesday 16 to Sunday 28 October.
An official announcement of her stayed was made recently which stated how she has been staying with the couple for a good part of summer in Oxfordshire, Doria enjoy a close relationship with Harry and continues to be a pillar of strength for Meghan.
The royal couple have since attended a charity performance of West End musical Hamilton and were guests of honour at the WellChild Awards in London last week.
While she was initially hesitant about the idea, writing on her former blog The Tig that she asked herself "Could I campervan?"
More information about their trip will be released closer to their arrival.