The Greens will choose a replacement for Metiria Turei next year, and Swarbrick had been tipped as an outside chance.
A leadership bid would not have been completely out of the blue. Male co-leader James Shaw took on the top job just eight months after becoming an MP.
With Swarbrick out of the frame, the job is likely to be contested by more senior MPs Marama Davidson, Julie Anne Genter and possibly Eugenie Sage.
Swarbrick's head is still spinning from her rapid political rise. Only a year ago, she came from nowhere to place third in the Auckland mayoralty race after a running a low-budget, social media-driven campaign as an independent candidate.
"It hasn't really hit yet," she said, after the Greens' election result of 5.9 per cent made her the youngest MP in 42 years.
The 23 year-old said she believed her youthful idealism could survive the cynicism and rough-and-tumble of Parliament.
"We have never allowed ourselves to be crushed by the status quo," she said.
"I'm really happy and privileged to be surrounded by a team which believes in idealistic notions about a better world and a better Aotearoa where every child grows up out of poverty.
"It may sound idealistic, but you can be both idealistic and pragmatic and we have the policies to back that up."
When she joined the Greens, she spoke about wanting to solve the age-old problem of getting more young people to the polling booth. That has not eventuated, and she conceded that lifting the youth vote was "a project that will take some time".
She wants civics education in schools, funding for public interest journalism, and for politicians to build up more trust with the community.
Asked what roles she wanted in the Green Party, she picked the unglamorous, low-profile portfolio of local government.
"I think the best form of change we can bring about in New Zealand society is ... basically to rebuild communities. And I think getting people engaged at a grassroots level is a way to achieve that."
Not just young
Swarbrick was born and raised in Auckland, and had a short stint living in Papua New Guinea where her father was working as a consultant.
She went to Epsom Girls' Grammar and studied law and arts at the University of Auckland before founding a digital marketing business.
While studying she worked for student radio station bFM, where she tried and failed numerous times to get Prime Minister John Key on her shows.
Aged 23, Swarbrick is reluctant to be pigeonholed as a youth politician, but says she will bring a young person's perspective to national politics.
She has a $43,000 student loan, she is locked out of the Auckland housing market, and doesn't own a car.
"I have grown up seeing the wheels fall off an economic system which exploits both people and the planet," she told reporters today. "That life experience speaks for itself."
