Girouard worked for Country Life magazine from about 1958, firstly as its Architectural Writer, and then from 1964 as its Architectural Editor, until 1967. He was Slade Professor of Fine Art from 1975 to 1976. He was elected a Fellow of the Society of Antiquaries of London in 1987. He has been on the Board of Trustees of The Architecture Foundation.
His Life in the English Country House won the Duff Cooper Memorial Prize for 1978 Life in the English Country House - Girouard, Mark - Yale University Press, and the WH Smith Literary Award in 1979.