Laya Healthcare is set to hike its premiums by an average of 6.5% for its 700,000 customers from the start of October.
The company said the price rise was needed to address the increased demand for healthcare services and rising costs.
Today's announcement follows a 7% price increase in April.
The insurer increased premium rates twice last year - in October and April.
"While advances in modern healthcare, including new technologies and high-cost drugs are delivering better outcomes for our members, they are significantly driving costs up, particularly in private and hi-tech hospitals," said Dónal Clancy, Managing Director at Laya Healthcare.
"A pricing and product review is needed in order for us to meet the current and future needs of our members," he added.
Laya said more of its members are accessing more healthcare services than ever before.
In the first half of this year, it has seen an 11% increase in private hospital claim costs when compared to last year.
It said this was driven in particular by an increase in both cardiology and cancer claims, and high cost drugs.
"We continue to prudently manage claims, including extensive claim cost management to ensure that our members are getting the most appropriate care in the most appropriate setting for their needs, and at a price that’s sustainable and help keeps health cover affordable for our members", Mr Clancy said.
Laya also announced a number of benefit changes to be introduced to hospital excess and shortfalls across a range of plans.
It said these changes will be communicated directly to impacted members ahead of their renewal.
Among the changes, a 'per visit' excess will be introduced on the QuickCare benefit that gives fast access to treatment for minor injuries and illnesses in approved centres, including Laya’s own network of Laya Health & Wellbeing clinics.
The insurer said excess amount will vary depending on the scheme and level of cover of customers.
The Health Insurance Authority said while its aware these price increases may have an impact on some consumers, the health insurance market in Ireland is an open market, and insurance providers can make price changes as they see fit.
"These prices are based on the cost of the claims that the insurers receive," it said.
"There have been a number of health insurance price increases across the market in the past 12 months which is attributed to medical inflation and an increase in claims."
"According to our latest Annual Market Report, the total level of claims paid by insurers in 2023 rose by 15% on the previous year, and there was a slight increase in claims for private hospitals."
The HIA added that consumers are free to move to any plan on the market at their renewal date, and it encourages everyone with health insurance to review their policy each year to make sure that they are on the right plan for their current lifestyle and health needs.
