Mr Shaw, who also served as climate change minister for the six years of Jacinda Ardern's government, will leave the post in March.
The 50-year-old cited the passage of the Zero Carbon Act, which committed NZ to reducing emissions by law and created an independent Climate Change Commission, as a major highlight.
"I am very proud of the what the Greens achieved on my watch," he said.
"New Zealand can be proud that it has an enduring climate change framework, with long-term targets and institutions that will guide us over several decades and changes of government."
Mr Shaw presided over a period of historic support for the Greens, including a record 11.6 per cent result at the 2023 poll.
"Now is the time for a new co-leader to work alongside Marama (Davidson) to take this new Caucus into the future," he said.
However, the moderately-minded former consultant often lacked support from grassroots members of the left-wing party.
In 2022, members failed to endorse Mr Shaw to continue as leader at an annual confidence vote, only for him to continue on when no other MPs stood against him.
The favourite to succeed him as co-leader, alongside continuing co-leader Ms Davidson, is Chloe Swarbrick.
The 29-year-old political sensation became the first Greens MP to successfully hold a seat when she defended Auckland Central from both the National and Labour parties at the 2023 election.
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