Kensington Palace confirmed the couple would spend one night, October 18, in Melbourne.
Afterward, they should be arriving in Nuku'alofa, Tonga for a brief visit, only to then return to Sydney and wrap up their tour in New Zealand.
The five nurses who attended the award ceremony in London were photographed with the Duke and Duchess of Sussex.
The Duke and Duchess will arrive in Wellington on Sunday 28 October and will visit Abel Tasman National Park on Monday 29 October.
Meghan's mother made her visits from Los Angeles after 74-year-old Thomas repeatedly criticised the former actress for "cutting him off" as they have not spoken since the day after the royal wedding, which the retired lighting director missed due to undergoing heart surgery.
"I look forward to welcoming The Duke and The Duchess of Sussex to Australia next month".
The pair got married earlier this year in May and the New Zealand visit will be a part of their first major tour outside the United Kingdom.
According to Kensington Palace, Their Royal Highnesses were invited to tour the Commonwealth Realms of Australia and New Zealand by the countries' respective governments and were asked to tour Fiji and Tonga at the request of the Foreign and Commonwealth Office.
Prince Harry and Meghan Markle are to visit New Zealand in October as part of their first global tour outside of the United Kingdom.
The focus of their royal tour is on youth leadership, environmental and conservation efforts, including the dedication of several new Queen's Commonwealth Canopy projects.