Endeavour Automotive has bought Regent Automotive in a share capital deal.
Regent Automotive operates the Volvo franchise in six locations in and around London.
John Caney, managing director of London-based Endeavour Automotive, said: "The acquisition is a perfect fit for us in terms of geography and is a major step forward in delivering our strategic plan of growing a regional group with a balance of manufacturer representation.
"Together with our Hyundai businesses turnover will be moving towards the £100 million mark, a commendable position with Endeavour having been formed just over two years ago.
"Regent Automotive is a fantastic operation with a loyal team of staff and I look forward to welcoming them and building on the success already achieved. This is a very exciting time to be joining the Volvo brand with the imminent launch of the all new XC90 and their continued aspirations for future success are a shared objective to that of Endeavour."
To enable this vision, Caney has expanded the current Endeavour board to bring a "wealth" of industry experience including Andrew Dick and Nick Bramham, both of whom were previously from the Wayside Group and Andrew Shackleton, from Grant Thornton.
“The new board offer a great deal of experience and will help drive the integration of Regent Automotive whilst delivering on the groups continued growth strategy," Caney said.
The current board of Regent Automotive, including managing director Tracey Perry, stepped down with effect from October 1. However, the current dealership profile and existing management team will be unaffected, said Caney.
Regent Automotive Group was the largest Volvo approved dealer group in the South East with dealerships in North, West, East and central London, Gerrards Cross and Watford.
Volvo Cars London was created following a management buy-out of three sites in January 2009.
Managing director Tracey Perry led the negotiations, alongside fellow directors Frank Fisher and Barry Green.
In July 2014 it sold its first dealership outside London, in Bishops Stortford, to Marshall Motor Group.