Mr Mohammed told the BBC the letter brought him to tears, as the Duke of Sussex had shown “genuine compassion and care” for the people of Nottingham.
He said: “It really touched the trustees, the volunteers, our service users and staff, that ordinary people like us are supported by some of the world’s most important people.
“It was a life-changing amount of money to people in the city of Nottingham.”
The charity, which is based in Gamble Street, said it provided more than 1,300 emergency food parcels every month and served more than 1,200 hot meals from its community hub.
Mr Mohammed said the number of people in need in Nottingham “shot up” during the pandemic and had got “worse” due to the cost-of-living crisis.
“Many of our service users are working people who are struggling to make ends meet and unable to afford the basics, like fresh produce, toilet roll or toothpaste,” he added.
The director said the donation had also allowed the charity to buy new equipment for its community centre, which provides hot meals every Monday, Wednesday and Friday.