Graydon received his early education at S.S. No. 6 Chinguacousy in the County of Peel, Ontario. He attended Brampton High School, and was a student at University of Toronto in Political Science. He graduated from Osgoode Hall in 1924. He then became a partner of the late Justice William Raney, one-time Attorney General of Ontario.
In 1933, at the age of 36, Graydon became the President of the Peel County Conservative Association. He was the youngest man ever to hold that position. In 1934, he helped rejuvenate the Conservative Party of Ontario by forming Young Conservative Clubs at a time when the party's existence was threatened. Optimism, confidence, acumen and an appealing manner were some of his assets.
Graydon was Opposition Leader in the Canadian House of Commons from 1943 to 1945 because John Bracken, the new leader of the Progressive Conservative Party of Canada, did not have a seat in the House, and chose not to seek one until the 1945 federal election.
It was said that he was well liked in Quebec, admired by the Irish and the agrarians who were a force in Graydon's formative years.
In 1945, he was Canadian delegate to the San Francisco World Conference, and delegate in London, representing Canada on the Preparatory Committee of the United Nations. He was Alternate Delegate for Canada at the UN's 1st General Assembly 1946, Parliamentary advisor to the Canadian Delegate to the UN General Assembly in 1950 and in New York, 1952.
He was a member of Grace United Church, Brampton, of several local lodges, including Campbell's Cross Loyal Orange Logde of the Board of Regents of Victoria College and of the Peel War Records Board.
He remained Member of Parliament for Peel until his death in 1953.
A high school in Mississauga has been named in his honour. A senior public (junior high) school in Brampton, Ontario also bears his name.
- Gordon Graydon – Parliament of Canada biography
- Gordon Graydon Memorial Secondary School - Mississauga Ontario