Prentis Donegan Partners and Price Forbes are to merge their wholesale insurance broking and underwriting management businesses.
The merged organisation will operate under the Price Forbes name.
Terms of the agreement were not disclosed.
Price Forbes chairman Simon Fisher will continue as chairman of the merged company, while Prentis Donegan chairman Michael Donegan will become chief executive officer of Price Forbes.
The merged company will have gross written premiums of approximately $585m, and a staff of 175.
Price Forbes said the merger would more than double the size of the group's wholesale presence in the Lloyd's, London and Bermuda markets.
Jeremy Cooke, president and chief executive of the Price Forbes group, said: “This transaction is a first step in growing the group's wholesale presence globally and demonstrates our commitment to serving independent clients.
“We are very excited about the opportunity to combine these two very distinct, yet complementary brokers.
“The combined operation will greatly enhance our ability to serve both existing and new clients with a broader range of products and a larger team of professionals.”