Paradigm Norton has entered into a merger agreement with The Red House Consulting, expanding the firm into London.
The merged financial advice firm will employ 55 people across offices in Bristol and Torquay, as well as the capital.
Barry Horner, chief executive of Paradigm Norton, said his firm's clients are located along the M4 corridor, so he had been looking to build a London office for several years.
He said: "We are absolutely thrilled to be merging with The Red House, a firm we have watched for a number of years, who share our values, passion and commitment to delivering an excellent client experience."
Paradigm Norton was founded in 2001 while The Red House was founded in 2007 and the combined business will use the former's name.
Ruth Sturkey, managing director of The Red House, said: "We are delighted to be joining forces with Paradigm Norton, a firm we have known and admired for nearly 10 years.
"This merger is great news for both our clients and our team, bringing greater strength, depth and continuity to our offering.
"The integration of our teams, each of whom have an excellent track record of delivering innovative financial planning solutions, gives our mutual clients a range of additional resources, expertise and life skills."