Quinn Healthcare has announced an average price increase of 12% from 1 January 2012.
The increase will be applied to existing customer policies on their renewal date.
The company says the move is partly due to the Health Insurance Levy, which cost the business over €100m in the last two years.
It has also blamed an increase spend on public hospital cover, as well as increased volumes and higher costs.
The Irish Patients' Association says it is the latest in a series of price increases in the sector and could be a tipping point for health insurance customers.
Quinn Healthcare policies already rose by almost 8% in January and 6% in April.
The VHI also had two price rises this year and Aviva increased the price of its policies by 14% in March.
