After announcing the relaxation of the country's tight border controls, Ardern developed symptoms on Friday evening and returned a positive test before a positive result from a rapid antigen test on Saturday morning, her office said in a statement. Her symptoms are said to be moderate.
Her partner, Clarke Gayford, tested positive last Sunday, and Ardern has been in quarantine since then.
She will have to isolate until the morning of May 21 and will not be in Parliament until the end of the week when her government has two set-piece events in the emissions reduction plan on Monday and the budget on Thursday.
Ardern will carry out some duties remotely, but her deputy Grant Robertson will take the regular post-cabinet press conference on Monday.
This is a milestone week for the government and I am gutted that I can't be there for it, Ardern said.
Our emissions reduction plan is designed to meet our carbon zero goal and the budget addresses the long-term future and security of New Zealand's health system.
My family is no different this year because I said earlier in the week that isolating with Covid 19 is a very Kiwi experience.