"In addition to size and expertise, they were also one of the leading Holden dealers in the country and bring great experience in continuing to support Holden customers with the highest levels of service whilst bringing new brands into the sales operation," Howarth said.
"We have just brought in one of Europe's best-selling brands in Renault, and there'll be more to come."
An Ebbett Group spokesman said the idea of joining up came "organically" as a good relationship between the businesses formed while working in the Holden network.
Ebbett was established in Waikato in 1928 and has twelve dealerships around the North Island.
Ebbett Group managing director Ben van den Engel said Karamu Holden was a "really good culture fit" and gave it valuable presence on the East Coast.
"This is a good deal for both businesses."