She made her views clear through what she did not say rather than what she did.
Asked about Trump, she would instead offer her own views on a particular topic. The subtext was that they were diametrically opposed to his, but that was left to others to deduce. She did not spell it out.
Her week in New York was a test of her foreign affairs chops, a fast-paced one.
Former PM Helen Clark loved the often arcane rituals and language of diplomacy, and Clark's successor John Key grew into it but relied more on building personal relations with foreign leaders rather than traditional diplomacy. It worked for each of them.
Ardern is still finding the way to her own style and in New York was necessarily cautious - if possibly overly so.
She gave no chances for tubthumping headlines, recognising that even a gentle direct rebuke of Trump would result in one.
She is building her own links, helped by an apparent flux of leaders of similar age to her coming into power - such as Austria's Sebastian Kurz (32), Ireland's Taoiseach Leo Varadkar (39), Colombia's President, Ivan Duque (42) and Spain's Prime Minister Pedro Sanchez (46).
It will be helpful when it comes to the EU trade agreement that most of those are from the European Union countries.
Ardern and baby Neve arrive at United Nations headquarters. Photo / AP
Baby Neve was undoubtedly an icebreaker for her, but Ardern also set about doing business for herself. Climate change is shaping up to be a key area for her to try to shine on the international stage when it comes to substance.
In that respect, French President Emmanuel Macron has helped out by involving Ardern in his own attempts to set up an international grouping of leaders to push ahead with climate change measures.
Ardern went to more climate change related events in New York than any other international issue - although she was careful to target her bilateral meetings around trade and ensure it was not neglected totally.
Ardern also pushed on women's rights. The line that got her spontaneous applause during her address at the UN General Assembly was "Me Too must become We Too".
Ardern used it just after she spoke about women in countries where human rights were not so well recognised as in New Zealand.
At the other end of that scale on both climate change and women's rights is the man whose name she will not mention, Donald Trump.
Asked about those differences, Ardern's response was that she was sticking to long held values. "It's just the values of those around us have changed over time."
The message to Trump in those silences? It's not me, it's you.
