The eldest son of Byron Cary, 12th Viscount Falkland and his wife Mary, Cary was educated at Eton College and the Royal Military College, Sandhurst.

[3] Cary was seconded to the 3rd King's African Rifles and stationed in Nairobi from 1903 to 1905.

[5] Cary then served as Deputy Governor of Wandsworth Prison until 1914, when he returned to the Guards as a captain in the 1st Battalion for the duration of World War I.

He then entered the Reserve of Officers and was breveted major on 1 January 1919,[6] and made an Officer of the Order of the British Empire on 3 June 1919, due to his war services.

[7] He succeeded to the peerage on the death of his father in 1922, and was elected a representative peer for Scotland, sitting in the House of Lords until 1931.