In a valedictory letter to Ms Ardern, Mr Lee said he was sorry to learn that she had decided to step down, although he fully understood her reasons for doing so.
“Like many, I was moved watching your personal and sincere statement announcing your decision,” he said.
“I hope that after you have handed over your duties, you will be able to recharge your tank and continue contributing to public life in other ways.”
Mr Lee wrote in his letter that Ms Ardern had steered New Zealand through unprecedented and challenging times.
She led the country with “kindness, compassion and strength through multiple crises”, including the Christchurch attacks, the White Island eruption and the COVID-19 pandemic.
“You have also been an inspiration, especially to women and girls, not just in New Zealand, but across the world. You have demonstrated that empathy and courage can go hand-in-hand in political leadership,” said Mr Lee.
Relations between Singapore and New Zealand were strengthened during her time as prime minister.
The Singapore-New Zealand Enhanced Partnership was launched in May 2019 during Ms Ardern’s first official visit to Singapore.
During her second official visit, the partnership was expanded to include cooperation in climate change and the green economy.
“I have always enjoyed our conversations, such as when we exchanged notes on how to manage the COVID-19 pandemic, as well as on regional and international issues,” said Mr Lee.
“You have been a very good friend of Singapore. Please know that you and your family are always welcome in Singapore. I wish you, Clarke and Neve all the best,” he added.