Cornmarket Group Financial Services had agreed a deal to buy independent broker Penpro Ltd.
Penpro specialises in the administration of group life, income protection, serious illness and other schemes to members of the Garda Representative Association, army officers and other groups within the public sector.
It was first set up in 2005 by its current managing director and owner Martin Sheehan. He will join Cornmarket to ensure a smooth transition of the business.
The deal, which is still subject to regulatory approval, is expected to be completed by early August.
Cornmarket provides income protection, retirement planning, group life and serious illness insurance, health insurance and car and home products to over 400,000 policyholders.
It currently administers over 50 union, association and employer endorsed schemes.