Outside of his professional life, Douglas Hartree was passionate about music, having an extensive knowledge of orchestral and chamber music. He played piano and was conductor of an amateur orchestra. This passion for music was perhaps what brought him together with his wife, Elaine Charlton, who was an accomplished pianist. Their marriage resulted in two sons, Oliver and John Richard, and one daughter, Margaret. He died of heart failure in Addenbrooke's Hospital, Cambridge, on 12 February 1958.