Leith's is part of the sport, leisure and fine dining division of the Compass Group, and will cater exclusively to Beaulieu's conferencing and banqueting and major event division, with mobile units and bars.
Beaulieu's venues include the National Motor Museum which houses a collection of contemporary and classical cars. Other venues across the Beaulieu estate include Palace House, its conference and banqueting facility Domus, adjoining Beaulieu Abbey and restaurant The Brabazon.
Leith's managing director Nick Moorhouse said: "We're proud to be operating at Beaulieu. As centres of historical and social significance, the choice of venues is truly inspiring and we are very confident that our catering matches such high standards."
Beaulieu Enterprises managing director Russell Bowman said: "We are delighted to have signed this agreement with Leith's and look forward to working with it to further enhance the service we offer to all of our customers."
Palace House is still home to the Montagu family and is available for hire to private dining events, and the Domus can host corporate medieval feasts.
The National Motor Museum can accommodate 1,000 guests for canape reception events.