On 11 January 1899, Mason married Mary Margaret, a daughter of the Rev. G. J. Blore DD, honorary canon of Canterbury Cathedral and a former head master of King's School, Canterbury. They had two sons, Paul and Lancelot, and a daughter, Mildred. Paul became a diplomat and was ambassador to the Netherlands in the 1950s, while Lancelot followed his father into the church and was archdeacon of Chichester from 1946 to 1973.
