Wellington and nearby areas were shaken by a 5.8 magnitude earthquake with the epicentre 30 km northwest of Levin, a city close to the capital, and at a depth of 37 km, according to Geonet.
Ms Ardern was speaking on a live TV interview at the time from the parliament building, called the Beehive.
“We are just having a bit of an earthquake here, Ryan... ,” she told the host of the show Ryan Bridge, as she, the camera and other things around her shook.
“Quite a decent shake here... if you see things moving behind me. The Beehive moves a little more than most,” she said.
Ms Ardern assured the host that she was safe and the interview resumed.
The video was soon viral on social media.
Why am I not surprised that Jacinda Ardern casually takes an earthquake interrupting her interview in her stridepic.twitter.com/mq4h6LuTfC— 🇳🇿 • eloise • 🇫🇷 (@reyloise)May 24, 2020
There were no damages and no injuries, Ms Ardern confirmed at a news conference later, but the shaking that lasted for more than 30 seconds caused panic in Wellington with several people in offices and homes getting under their tables for cover.
New Zealand lies on the seismically active “Ring of Fire”, a 40,000-km arc of volcanoes and ocean trenches girdling much of the Pacific Ocean.