Focus Financial Partners LLC is investing in Boston-based registered investment advisory firm (RIA) The Colony Group, which has approximately $1.3 billion in assets under management, Focus company officials said today.

The partnership, effective Oct. 1, will increase Focus' assets under management by $9 billion.  Details of the deal were not disclosed.

Launched in 2006 with four partner firms and $3.5 billion in assets under management, Focus has now acquired 19 partner firms and has $45 billion in assets under management.

"We believe it is an opportune time to partner with Focus, which has the proven ability to help firms like ours move forward into their next evolution," says Colony CEO and president Michael Nathanson. "With Focus' support we will be able to go farther faster, allowing us to realize our full growth potential."

Focus founder and CEO Rudy Adolf say the company's Colony partnership strengthens the company's partner model.

"Colony is simply one of the best independent investment advisors in the market and we are thrilled to be partnering with them," Adolf said. "We look forward to adding more high-caliber independent, fiduciary-minded advisors in the months and years to come."

With over 40 employees, Colony provides wealth management services, including investment management, tax planning and preparation, as well as corporate advisory services. The firm serves over 800 clients including high-net-worth individuals, families and institutions.

Kirby Hamilton founded Colony in 1986 to provide customized, objective financial services. Hamilton will step down as chairman following the close of the transaction. Going forward the Colony management team will consist of a three-member board including Nathanson as chairman, Stephen Sadler, president of Colony Wealth Management, and Elisabeth Talbot, executive director and chief market strategist.

In addition to the firm's Boston headquarters, Colony has offices in Naples and West Palm Beach, Fla., and Washington, D.C.

-Jim McConville