Finning paid £3.1m for the assests of the Lisburn business and takes over as the official dealer for Cat in Northern Ireland.
The deal is also expected to save more than 50 jobs.
Discussions are also at an advanced stage with the receiver covering the dealer’s business in the Republic of Ireland.
Finning said it anticipated these talks would be concluded shortly.
McCormick MacNaughton went into administration in June after suffering financial difficulties.
Neil Dickinson, managing director at Finning UK said: “As part of this agreement, we acquire an active power systems portfolio, as well as access to opportunities in construction.
“We look forward to providing unrivalled service to customers in our new territory.”
Mike Waites, President and CEO of Finning, said that the company was pleased to add Northern Ireland to its established UK operations.
He added: “We will be able to leverage our existing infrastructure and service expertise to complement our UK dealership.
“Being awarded the dealer territory for Northern Ireland speaks highly of Finning’s relationship with Caterpillar.”