If the Greens end up in a coalition Government, they want half their Cabinet ministers to be women.
And co-leader James Shaw says he'd call on other parties in the coalition to do the same.
"Just 30 percent of Cabinet positions are currently held by women, and only 32 percent of MPs in Parliament are women," Mr Shaw said.
"If political parties are serious about ensuring women across all workplaces are paid more and given the opportunity to take on senior roles, then political parties should start by getting their own houses in order.
"A Government with 70 percent of its ministers men isn't good for women and it isn't good for New Zealand."
The plan would only apply to Green Party ministers around a cabinet table, not the wider Cabinet.
But Prime Minister John Key says National won't bring in a quota for women in Cabinet, and having one does a disservice to them.
"They imply the reason they get a job is because they're female. Actually, the women we've had to lead our country, lead our judiciary, our biggest companies, or our Governor General have been better or as good as any man that could have done that job.
"People should hold a warrant and be responsible as a Cabinet minister because they're the best person for the job," he said.
Mr Key says he wants more women in his Cabinet and in Parliament generally.
"We're actively encouraging more women to join our caucus and for us to have a pipeline of people we can promote to Cabinet.
Having more women in Parliament means it is more likely they will be chosen for senior positions, he said.
Mr Shaw made his announcement at the Council of Trade Union's annual conference, and won immediate praise from the CTU's women's council.
"It's wonderful that the Greens are taking a lead in guaranteeing equal representation of women in their own ministerial line-up," said spokeswoman Sheryl Cadman.
"Gender does matter - more women in Parliament focuses attention on making our country better for all."
3 News / NZN