The group will tackle grounds maintenance and horticultural services for Warwick District Council until 2020. There is potential to extend to 2028, which would make it a 15-year deal. The contract is worth around £900,000 a year.
The council's landscape areas include five major parks and green spaces on housing estates and next to roads as well as extensive naturalised areas. It is due to become a centre for excellence on bowls.
Jephson Gardens and Mill Gardens have Green Flags and the group will work with the council to draw up management plans for other parks to achieve Green Flag status. The Landscape Group boasts 36 flag parks within its portfolio of UK sites.
Landscape Group director Sarah Hughes-Clarke said: "We were chosen following a competitive tender process to work with a district famed for its historical significance and beautiful green spaces. We were keen to demonstrate our horticultural expertise.
"But we will provide more than basic grounds maintenance and do this by working with local groups."
Last month, the company won big contracts in Mendip and with Hastings Borough and Rother District Councils.