"We are trialling cover for travellers with existing mental illness at this stage because we want to get it right and give people with mental illness a fair deal and effective care."
Emmett said the trial would run for six months although it may be extended depending on the volume of applications which it received.
The extra premium cost would vary depending on the individual's circumstances, where they were going and how long for, he said.
"It is not possible to generalise on an average amount except to say it will be fair and reasonable."
Mental illness has until fairly recently been excluded from travel insurance policies in New Zealand.
A spokeswoman for Southern Cross Travel Insurance said it lifted its general exclusion for mental illness in October 2016. She said the company treated mental illness the same as physical illness.
People with a pre-existing mental illness can apply to be covered for claims relating to the illness while travelling if they undertake a medical assessment and pay a premium.
A spokesman for World Nomads Group which underwrites the Warehouse travel insurance said it had an exclusion on mental illness.
But it used its discretion and if someone had a legitimate claim involving mental illness it would pay out.
He said the company had taken that approach in the last year and had paid out on hundreds of claims as a result.
The spokesman said it planned to change its policy in the future but had to do it in a way which did not allow for fraudulent claims as that would push up the policy costs for all users.
Emmett said a change in its ownership had enabled Cover-More to alter its policy.
"We took the opportunity when we changed underwriter to Zurich in Australia and New Zealand from 1 June 2017 to introduce the cover."
Zurich acquired Cover-More Group in April.
Emmett said the company's goal had always been to develop a solution for mental illness cover that was fair to all customers.
"There is a balance between providing cover for people impacted by mental illness when they travel, while offering a product to our customers that is reasonably priced and helps them to keep travelling."