She added that Johnson has an affinity with New Zealand, having travelled here previously.
Johnson, when he was Foreign Minister, visited New Zealand in 2017.
Ardern said New Zealand and the UK already share a commitment to launch negotiations towards a comprehensive and high-quality free trade deal once the UK leaves the EU.
This, she said, was something that was discussed at the UN Leaders' Week in New York earlier this year.
"Our many other common interests position us well to work together globally, including in the Pacific region and on climate change," Ardern said.
National Leader Simon Bridges has offered UK Prime Minister Boris Johnson his warmest congratulations after his decisive election victory.
"Boris Johnson is a firm friend of New Zealand," he said in a statement tonight.
The pair met when Johnson was in New Zealand in 2017.
"Significant opportunities exist for our countries to do more together post-Brexit," Bridges said.
Bridges conveyed his best wishes to Johnson and the UK Government.
"I look forward to the continued development of our countries' friendship and am excited to work with you in the future."
The news will no doubt be welcomed by Foreign Minister – and self-described friend – of Johnson, Winston Peters.
Peters threw his support behind Johnson to take over the leadership of the Conservative Party in June this year after former leader Theresa May stood down.
Peters likened Johnson to former UK Prime Minister Winston Churchill and said he had what the people of the UK want – "character and courage".