The financial terms of the deal were not disclosed.
The Middle East firm’s £280m ($338m, $305m) in client funds will move over to the Blacktower Group’s advisory platform.
All PWS Group staff including chief executive Craig McConnon will join Blacktower.
PWS advises on British pensions, overseas pension transfers, lifetime allowance tax planning, inheritance tax planning and wealth management.
Blacktower said that this deal is part of its “vertically integrated growth plans” and is “the first of many agreements under consideration, with further announcements to be expected in the coming months”.
John Westwood, group managing director of Blacktower, told International Adviser: “The clients based in UAE with PWS will naturally move into Blacktower under the deal.
“We also have other interests in this jurisdiction which means an expansion is under review.
“Blacktower is currently looking at obtaining licences to expand its operations in the Middle East.
“Blacktower has received an increasing number of enquiries for firms based in the UAE looking for licensing solutions and other business support. As such, we anticipate significant growth in the region from both organic growth and M&A activity.
“An acquisition of this size will require an element of restructure. As part of this, PWS’s current set up is being reviewed to ensure a smooth transition in line with the existing offices and infrastructure already in place at Blacktower Group.”
PWS’ McConnon said: “The merger between our respective organisations made complete sense at group level, but more so for our valued clients, both existing and future.
“International clients rightfully demand high standards of advice and positive outcomes in their financial planning arrangements.”
In 2017, PWS Group decided to close its Qatar office following the completion of its annual strategic business review, which came just after it opened operations in Dubai and Barcelona.