UK company AAB has acquired Cork-based chartered accountants O'Connor Pyne & Co, which employs 65 staff.
Last year the British group bought Dublin-based Ormsby & Rhodes.
AAB now has revenues of annual revenue of €120m.
The latest acquisition means it will boost its revenue by €20m and it will employ a total of 200 people in Ireland.
O'Connor Pyne & Co was founded 20 years ago and has links with Munster Technological University.
"This investment allows us to build scale in Munster while broadening the services and specialist expertise available to clients in the region," Emma Lancaster, the chief executive of AAB, said.
