Mr Fothergill's donates 25p to the Royal Hospital's charity from every packet of 250 seeds priced at £1.99 it sells through its retail stockists.
The Suffolk seed company has said it will continue to support the organisation until at least the centenary of the end of World War One in 2018.
Rachael Ferguson, corporate partnerships officer of the Royal Hospital Chelsea, was presented with a cheque by the company's David Carey for £15,360.75, the value of sales so far in 2015, when she attended Mr Fothergill's annual Press Day in August.
Mr Fothergill's commercial director Tim Jeffries said: "We are thrilled about our links to the Royal Hospital Chelsea. It an inspiration, from its caring staff and impressive setting to the Chelsea Pensioners themselves. Our staff and the nation's gardeners are committed in their efforts to raise money, and it is heartening that our retail stockists also want to know how much we have raised together for the cause."