Prime Minister Jacinda Ardern made the announcement on Sunday after cases of community transmission were reported.
The three cases, confirmed earlier in the day by the health ministry, were from the same household in South Auckland.
All the patients are currently in quarantine.
“As of 11:59 p.m. Sunday February 14, Auckland will move to (Alert) Level 3 for a period of three days until midnight on Wednesday.
“The rest of New Zealand will move to Level 2 for the same period of time,’’ Ardern told reporters, adding that the decision will be reviewed on a 24-hour basis.
Since the outbreak of the pandemic, the country has confirmed a total of 2,330 cases, including 2,258 recoveries and 25 fatalities.
There are currently 47 active cases in New Zealand.