Stonehage Fleming will acquire the investment activities of Cavendish Asset Management and will take over the running of its range of four OEIC funds.
Family office Stonehage said that it would also take over all of Cavendish's client portfolios, including those run for institutional and professional clients as well as ultra-high net worth individuals and families, worth about £1bn.
The £425.8m Cavendish International, £72.1m Cavendish Opportunities, £70.1m Cavendish AIM and £18.4m Cavendish Balanced Income funds will be rebranded under the Stonehage Fleming name.
The managers of the four funds, including Paul Mumford, will join Stonehage and continue managing the mandates, while Cavendish CIO Julian Lewis will join Stonehage Fleming Investment Management CEO and head of investments Graham Wainer as co-chair of the firm's investment committee.
The deal is expected to complete on 1 August.
Lewis said Stonehage was "a highly successful firm with an outstanding… and client-centric approach and will provide an excellent home for our clients and our people".
Meanwhile, Stonehage's group CEO Chris Merry said the firm had "worked hard to build a relationship with Cavendish and its clients over many months".
"Notwithstanding the extraordinary environment, this is an important and exciting time for Stonehage Fleming," Merry continued.
"We have the scale, the range of services and practical wisdom developed over many years to be the partner of choice for wealthy families with complex needs."
Wainer added: "The families served by Cavendish have taken a positive decision to work with Stonehage Fleming as their investment advisor based on our broad proposition for families, the quality of our investment offering, and the strong cultural fit with our firm."