Kensington Palace said Maria Teresa Turrion Borrallo had recently started working with the family and confirmed she would accompany the Duke and Duchess and their son on the 10-day trip next month.
Ms Borrallo trained at the respected Norland College and her duties will include looking after George while his parents are away on planned visits to Queenstown, New Zealand and Uluru in Australia during the tour.
Reports in the UK suggested Ms Borrallo was in her mid-thirties and had been working for high-society families for two decades, with some branding her a "Spanish supernanny".
The Palace said in a statement it would not being giving further details on the new nanny or her appointment but said "the Duke and Duchess are of course delighted she has chosen to join them."
The couple had reportedly been looking to recruit a new helping hand with 71-year-old Jessie Webb, Prince William's former nanny, coming out of retirement to assist on a short-term basis.
There are likely to be limited opportunities for the Australian and New Zealand public to catch a glimpse of baby George, the third in line to the British throne.
It's likely William and Kate will show off their eight-month-old son a few days after landing in New Zealand and it's hoped there will be a second public engagement after the Cambridges arrive in Sydney on April 16.
The Duke and Duchess on Sunday April 13 will leave George with his nanny in Wellington and travel to Dunedin, Queenstown and Christchurch.
On Tuesday, April 22, the couple will stay in Uluru overnight, leaving their son with Ms Borrallo in Canberra.
