In a statement on Friday (Thursday in the Cook Islands), the Health Ministry said two new cases had been confirmed, bringing the total number to seven.
The Cook Islands government has launched Operation Namu25, which includes community clean-up across Rarotonga on Friday (Saturday NZT), vector control and spraying around areas with confirmed cases, and coordination with Pa Enua (outer islands) so they stay dengue free.
Local agencies, including island councils, are working together to support this national effort.
The Health Ministry said outer island communities were also preparing their own local response.
It said recent rain and humidity had increased mosquito activity.
"All clinics and health facilities remain alert and well-equipped to manage any further cases."
The ministry added the World Health Organization (WHO) and regional health partners had been informed.
There are no travel restrictions, but travellers are advised to take precautions.
"We urge everyone to help stop the spread of dengue in our communities," Health Secretary Bob Williams said.
"By working together, we can protect our families and prevent dengue from reaching the Pa Enua. Let's take action now."
