Whanau said her "absolute priority" at this stage was her new consultancy firm.
The Green Party has appointed Robin Campbell as Whanau's replacement, but she will remain in the role until the end of August to ensure a smooth transition.
Any contender for Wellington's mayoralty is yet to be confirmed.
Meanwhile, current mayor Andy Foster has been dancing around the question of whether he'll put in a bid for a second term for months now.
In April he told the Herald it was far too early for any official announcement about whether he intended to stand for the mayoralty again
He said he was enjoying the role and was fully committed to building a city with strong infrastructure, that's environmentally resilient, economically vibrant, affordable to live in and lots of fun.
"If people take that as a campaign opener, I am not going to argue", he said.
When asked the same question at the beginning of this month Foster said he is "committed to working with residents, colleagues, and stakeholders on opportunities that will ensue from the long term plan and spatial plan and the three waters initiative".
Foster would not say whether he intended on running.