The deal, with Maidstone-based Core Financial Services and worth £7.7m, is the biggest in AFH’s 27-year history.
Core’s boss Mark Sutton will join AFH, along with his team of nine advisers and their support staff.
The acquisition will add £230m to AFH’s funds under management, taking the group’s total to around £4.5bn.
Mr Sutton and colleagues started Core in 2004, and the company currently advises around 2,500 clients along the south coast and in Nottingham and London.
Mr Sutton, who has 30 years’ experience in financial services, said: “I believe AFH’s support expertise and service proposition mean we’ll be able to offer our clients a better service and better investment outcomes.
“And we’ll have more time to spend with our clients, sounds like a win-win to me.”
AFH chief executive, Alan Hudson, said: “This deal will significantly expand AFH’s position in the South East.
“I am pleased to welcome Mark and his team to AFH and I look forward to working with them to further the growth of AFH.
“It’s great to be celebrating our biggest deal since we started in 1990 and we’re not stopping here.”