Mrs Collins said granny nannies were often more flexible about after-school care.
"They often don't have families at home or husbands they have to get back for, so they can do Saturdays or for people who do shift work."
The Nanny Company specifically advertised for granny nannies because of their popularity, she said.
"Particularly in Christchurch since the earthquake, we're quite aware that parents want someone who knows what to do in certain situations and will keep their head, and so a lot of families like that maturity."
The company's oldest granny nanny had just turned 80.
Rockmybaby's greater North Island regional manager, Rachael Brough, has noticed an increase in the number granny nannies during the past six months.
"It may be that they've retired from their careers or previous fulltime roles and they're looking for some hours and a little bit more security."
She said "granny nannies" had usually raised their own families and were comfortable caring for other people's children.
"Quite often the grandmothers we get on board they do sporadic care for their own grandchildren so it complements having a nanny role and taking on other people's children. It's an extension of what they're already doing for their own families."
She said older nannies were not necessarily more popular than younger ones but they offered "a different kind of care".
"For example, I've had a couple of families who this year specifically asked to advertise for a grandmother babysitter, and that's because the children don't have grandparents. It's to have an older person in their lives."
Porse In-Home Childcare coach for Auckland Nicola Dunlop said older nannies were about getting back to family values.
"Families see it as a lovely caring-type scenario for their children."
The managing director of Auckland company City Sitters, Angela Jenkins, said older nannies were seen as "reliable, flexible and trustworthy, with great values".
Dream job for Jody, 60
Tim and Chanel Prestidge previously chose young nannies, but when they met 60-year-old Jody Bradfield they hired her straight away.
The Auckland couple are both paediatricians at Starship hospital and needed part-time care for their three children, Oscar, 6, Isla, 4, and Harry, 9 months, when they met Mrs Bradfield through KiwiOz Nannies.
The granny nanny, a school dental nurse for 40 years, began nannying in Britain a few years ago and loved it so much she pursued nannying when she and her husband returned to New Zealand.
Mrs Bradfield said working for the Prestidges was a dream job. Her adult children weren't ready to produce grandchildren yet and she had always loved young children.
Dr Prestidge, 36, said she and her husband were thrilled with the "extremely conscientious" Mrs Bradfield."She doesn't have a smartphone so unlike other nannies I see at the playground she's not checking her phone or Facebook every five seconds."
She also did washing, cooking and housework.
