The seventh and last son of an elderly clergyman from Pelynt in Cornwall, Grigson escaped a career with Colman's mustard to turn his hand variously to school teaching, journalism, broadcasting, radio monitoring (during the second world war), and radio production (he recommended the commentator John Arlott for the airwaves).

He was married three times; his first wife was killed by tuberculosis just before the second world war, and a mere handful of years before the disease became more curable. The second marriage ended in divorce. The third was to (in writer Jane Gardam's words) ' a large easy-going girl who wore tweeds and never worried about a thing', and lasted the rest of his life: this was Jane Grigson, later well known in her own right as a cookery writer. Jane 'ruined my figure, and saved my soul', according to her husband. A notable product of this marriage was their daughter Sophie, who, through her television appearances and writing on food and cookery, has probably achieved more exposure in the last ten years than either parent did in their whole lives.