Health New Zealand said it was linked to the initial case reported on Friday last week.
It brings the total number of cases of the highly contagious disease in the region to six, with another one confirmed but unrelated in Queenstown.
Both new Northland cases are close contacts who have been in quarantine while infectious.
There are also several new locations of interest, primarily in Queenstown and Cromwell in Central Otago, but also in Northland, following ongoing contact tracing efforts.
"While these cases in different parts of the country are unrelated to each other, both have links to recent international travel to countries experiencing outbreaks," National Public Health Services spokeswoman Dr Sharon Sime said today.
"So, it's an important reminder that for anyone planning to travel overseas, please make sure you are up to date with two doses of the MMR vaccine, which provides the best protection against measles."
It comes after health authorities warned anyone who went to a production at Kerikeri High School earlier this month to stay home to prevent the spread of measles.
Health NZ added a school play called Monsters, at 7pm on September 17, to its list of "locations of interest" - places where people may have been exposed to the virus.
It said anyone who attended the event but had not yet been contacted by public health staff should stay home and call Healthline urgently on 0800 611 116.
Sime said with school holidays continuing this week, it was a good time for parents and families to double check their immunisation status. It was particularly crucial for people in the Northland, Queenstown and Cromwell communities to monitor themselves for measles symptoms.
They include fever, cough, runny nose, sore eyes and a rash.
