Biden defeated Donald Trump on Sunday (NZ time) to become the next President of the United States after four days of painstaking ballot-counting across several battleground states.
Ardern said in a statement Biden was a "close friend of New Zealand" during his role as Vice-President during the Obama administration.
"The relationship between our two countries is strong, and I look forward to developing even closer relations with the incoming Biden administration," Ardern said in a statement.
"New Zealand will continue to work side-by-side with the United States on the issues that matter to both of us, including the prosperity, security, and sustainability in the Indo-Pacific and Pacific Island regions."
Ardern said Biden's campaign showed the shared interests New Zealand and the US have in addressing global challenges like COVID-19 and climate change.
"There are many challenges in front of the international community right now, the message of unity from Joe Biden positions us well to take those challenges on," she said.
The Prime Minister also acknowledged outgoing President Trump.
"New Zealand has enjoyed positive and cooperative relations with the United States over the period of the Trump administration, especially in the Indo-Pacific and Pacific Island regions," Ardern said.
Opposition leader Judith Collins also sent a message to Biden.
"Congratulations to Joe Biden and Kamala Harris on their victory in the United States," she posted to Facebook.
"New Zealand has an enduring relationship with the US which I want to see get even stronger. Let's get a free trade agreement done!"