He attended first Prince Edward School and then Rondebosch Boys' School in Cape Town, South Africa.
He was a Rhodes Scholar and read law at Hertford College.He held the posts of Minister of Defence in Rhodesia during World War II, Federal Chief Justice, acting Governor-General of Rhodesia from 21 November 1953 to 26 November 1954, and acting Governor-General of the Federation of Rhodesia and Nyasaland from 24 January 1957 to February 1957; he later resigned in protest from his Central African Federation (CAF) position, criticising the actions authorised by Sir Edgar Whitehead to suppress black nationalist opposition to the Federation in Nyasaland and Northern Rhodesia.Sir Robert Tredgold was named Privy Counsellor in 1957.
He retired to Marondera with his second wife, Lady Margaret Tredgold.
He published the book The Rhodesia That Was My Life in 1968.