Ardern, who is currently in Antarctica to mark Scott Base’s 65th anniversary, said she was grateful none of her staff were present at the time of the attack.
She said attacks on her office are not unusual.
“Look, unfortunately, from time to time we have such activities in our electoral office, that does not make it acceptable,” Ardern said.
Asked if she thought there was a greater risk of incidents like this happening again in the run up to election time, she said they had “quite a lot of activity constant”.
“Unfortunately, one thing I’ve observed is that we’ve had pretty consistent activity over the past couple of years. I can’t say if that will become more or less frequent as the election approaches,” Ardern said.
“It doesn’t matter what time of year it is. The people who work in our offices, they are there to do their job, they deserve to work in a safe environment.”
On Thursday, Labor Minister Willie Jackson condemned the online attack, saying there had been a “violent shift in political debate” in New Zealand from “normal and vigorous disagreement” to “theories of the messy conspiracy”.
He urged Kiwis to reach out to family and friends who may have convinced themselves of a “crazy secret plot”.