Jetstar has started charging A$50 for babies travelling on transtasman and international flights.
It has also introduced a A$30 ($32.30) fee for infants under 2 travelling on flights within Australia, although there remains no infant fee for New Zealand domestic flights.
Jetstar said this brought the airline in line with other transtasman carriers that already charge an infant fee. Air New Zealand, Qantas and Virgin charge 10 per cent of the full adult fare.
The new Jetstar charge includes an allowance for up to four over-sized items for infants, such as prams, strollers or portable cots.
"We know that fees and charges can be unpopular, but giving customers' choice and charging each customer for what they actually need helps us to offer the lowest possible fares, every day," the company said.
"That's how more than 22 million people flew on Jetstar for under $100 last year."