Ardern met with the leaders of Germany and France and got support for a free trade agreement. She was applauded in Paris when she explained that in seeking a greener future, New Zealand had stopped issuing new permits for offshore oil and gas exploration. And she was named in Time magazine as one of the world's 100 most influential people.
For many New Zealanders, an image defined the trip: Ardern wearing an indigenous Maori cloak and smiling as she and her partner Clarke Gayford arrived at Britain's Buckingham Palace.
But back home, Ardern faces political pressures.
Some people have criticized her oil and gas policy, including New Plymouth Mayor Neil Holdom, who said it was a "kick in the guts" for people living in the oil-rich Taranaki region.
A recent opinion poll indicated that support for Ardern's liberal Labour Party had slipped behind the conservative opposition National Party.
Asked Tuesday if she was worried she might be more popular abroad than at home, Ardern said it was of "no value or benefit" for her to be popular in places like the U.K.
"I need to focus on domestic issues and domestic politics and making sure I satisfy New Zealand voters," she said. "The rest is immaterial."
Ardern said one of her primary goals on her Europe trip was getting French President Emmanuel Macron to back the idea of a free-trade deal between the European Union and New Zealand.
Trade expert Stephen Jacobi said it was a significant diplomatic win for Ardern to get support from Macron ahead of an EU meeting next month to consider a mandate for such a deal.
"I think getting such a strong, unequivocal statement from the president was important," Jacobi said.
He said any deal is likely to take at least another two years to complete.
In an address last week to the Paris Institute of Political Studies, Ardern described how 10 years ago she was booed in a public meeting when she urged action on global warming, but that sentiments had changed: "My generation will be shaped by climate change," she said.
In Time magazine, Sheryl Sandberg, the chief operating officer of Facebook and author of "Lean In," wrote that the 37-year-old Ardern, who is pregnant, was changing the political game.
"In a world that too often tells women to stay small, keep quiet - and that we can't have both motherhood and a career - Jacinda Ardern proves how wrong and outdated those notions of womanhood are," Sandberg wrote.
Ardern has no more overseas trips planned ahead of her June due date. She intends to have deputy Winston Peters fill in for six weeks after she gives birth before returning to work.
Copyright 2018 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.