Described as a 'merger' by multi-disciplinary PM Group, the move means Devereux Architects - ranked 56th in last year's AJ100 - will now operate as a standalone brand within PM Group.
International projects include Gibraltar's General Hospital, two new hospitals on the Turks & Caicos Islands in the Caribbean, and a number of urban and masterplanning projects in Abu Dhabi in the Middle East.
The deal marks PM Group's first acquisition in the UK - it already operates offices in Rugby and Basingstoke.
Commenting on the deal, PM Group boss Pat McGrath said it would support the firm's expansion into a range of new sectors including healthcare and education in the UK, Europe and Asia and bring Devereux Architects' services to Ireland.
He said: 'It demonstrates our strategy to grow our presence in the UK market. Devereux's excellent track record puts PM Group in a strong position in light of the forecasted annual Eu2 billion (£1.3 billion) capital spend within Ireland and Northern Ireland in the public sector.'
PM Group employs 1,600 people across offices in Ireland, the UK, Poland, Russia and Singapore. In 2006, it had a turnover of Eu165 million (£113 million).
Nic Allen, managing director of Devereux Architects said: 'There is a real opportunity to develop a multi-skilled, multi-office architecture, engineering and project delivery capability in the UK, Ireland and across the group's existing business network.'