Raymond James UK Wealth Management is set to acquire the entire issued capital of Charles Stanley for £278.9m, at a price of 515p per share.
The terms of the acquisition represent a premium to the closing price of Charles Stanley shares as at 28 July of 43.5%.
Raymond James said it had "long admired Charles Stanley's reputation, heritage and its talented pool of investment managers, financial planners (collectively referred to as wealth managers) and professionals".
"The two firms share a common client-centric approach and both offer employed and self-employed affiliation models, while Raymond James also provides platform services, enabling the flexibility that wealth managers value. Charles Stanley meets Raymond James' historical acquisition criteria, in particular as an excellent strategic fit with a complementary culture," the announcement said.
According to the announcement, the acquisition will provide the two firms with the opportunity to accelerate the growth of their respective UK wealth businesses, with Charles Stanley bringing 200 additional wealth managers to the table.
Charles Stanley would add approximately £27.1bn in client assets, bringing Raymond James' total client assets in the UK to over £40bn.
Both firms are expected to vote in favour of the acquisition at their respective AGMs. The acquisition is dependent on shareholder support and regulatory approval.
Paul Reilly, CEO of Raymond James, said: "We have long respected and admired Charles Stanley and believe our proposal presents an extremely attractive opportunity to combine our respective UK wealth management operations.
"Raymond James will seek to leverage the respective strengths of Charles Stanley and Raymond James through further investment in technology, infrastructure and back office partnerships to enhance the firms' already strong offering in wealth management."
Paul Abberley, CEO of Charles Stanley, said: "The board believes that the terms of the Acquisition represent fair value and an attractive premium for Charles Stanley shareholders and therefore intends to recommend unanimously that shareholders vote in favour of the acquisition.
"Raymond James recognises Charles Stanley' reputation, heritage and talented staff, as well as our shared client-centric approach and compatible structures and cultures.
"Supported by the clear strategic rationale and intentions Raymond James has described today, I believe all stakeholders will benefit from the opportunities for growth arising from Charles Stanley becoming embedded within the Raymond James group."