The contract started on 1 November and will involve all aspects of grounds maintenance in amenity areas at the 26 mile long, 10,000 acre linear public open space which stretches from London into Hertfordshire and Essex.
Glendale managing director Andy Corcoran said: "This is a prestigious vital green space for the local community and visitors to the area and we are proud to be working in partnership with the
Park Authority in delivering its vision to be a world class leisure destination."
Lee Valley Regional Park attracts more than 4 million visitors a year and encompasses heritage sites, country parks, sports facilities, farms, golf courses, lakes and riverside trails.
Glendale regional director Adrian Wickham said the company's skills in conservation management would be put to good use in the park's varied wetland habitats."