The number of Kiwis over the age of 65 is projected to hit more than one million by the late 2020s.
Newly-released population projections from Statistics New Zealand show that one in five New Zealanders will fall into that category.
That will mean the number of people aged over 65 will exceed the number of children aged 15 years and under.
By 2036, the population aged over 65 will increase to 1.2 million and by 2061, it'll be 1.5 million.
"These trends reflect much lower fertility rates in recent decades, and people continuing to live longer," population statistics manager Andrea Blackburn said.
There are 600,000 people aged over 65 and 900,000 children in New Zealand's population of 4.4 million.
The population is projected to reach five million in the mid-2020s and six million in 2061.