Vertu Motors has exchanged contracts to acquire two dual franchised Ford and Mazda dealerships in Glasgow and Hamilton, Scotland, operated by Shields Automotive Limited.
The properties will be leasehold and bought with £2.5 million in cash.
The deal is expected to be complete on June 30.
In the year to June 30, 2009, the two businesses had a turnover of £27.1m.
This acquisition marks the group's third and fourth Scottish dealerships, all of which have been acquired in 2010.
Both will be rebranded Macklin Motors, which is Vertu's brand established this year for dealership acquisitions in Scotland.
This acquisition brings the total number of Ford dealerships operated by the AM100 group to 19 and total number of Mazda dealerships to four. It now operates 64 sales outlets in total.
Robert Forrester, CEO of Vertu Motors said: "We are pleased to have agreed to acquire a further four sales outlets in Scotland.
"This demonstrates continued delivery of our strategy to grow a scaled motor retail group across the country in targeted regions.
"We are excited by the opportunities this acquisition brings with our manufacturer partners, Ford and Mazda and both dealerships are in prime retail locations representing an excellent geographic fit with the group's existing Scottish dealerships.
"We will now have six sales outlets in Scotland and we look forward to continuing to grow the Macklin Motors brand."