He said New Zealand and Australia had an enduring relationship and alliance based on shared values such as respect for the rules-based international order, and had to work closely together in the Pacific.
In response, Ardern also nodded to the countries' common values and said it was telling that this was her third trip to Australia in her first four months as prime minister.
The two countries had a chance to strengthen their economic ties even further, she said.
Earlier today, Ardern and Gayford were officially welcomed with military honours at Admiralty House, the residence of Governor-General Sir Peter Cosgrove.
It was a quick walk next door to Kirribilli House for a press conference with Turnbull before heading to the Australia New Zealand Leadership Forum where Foreign Minister Winston Peters is making a star appearance this morning.
He is likely to be quizzed on an important speech he gave last night in Sydney in which he foreshadowed an increased diplomatic effort by New Zealand in the Pacific.
He wants to see great co-ordination in the interests of friends such as the United States, the EU and Australia to counterbalance the influence of other "external actors" - code for China and Russia.