Hendy Group has taken over three Honda dealerships on the south coast operated by Alan Day Group.
Alan Day had already sold a fourth Honda outlet in Hendon, north London, to Crown Honda in February, so it is now left with just one dealership in nearby Enfield.
Honda UK said this dealership is expected to remain with Alan Day.
Paul Hendy, managing director of Hendy Group, said all 80 staff at the Southampton, Winchester and Portsmouth dealerships will transfer to his group.
“The Hendy Group already operates a successful Honda dealership in Exeter and we are delighted to be expanding our Honda operation with three key new sites,” he added.