Stanfield was born to wealthy parents in Truro, Nova Scotia, of Stanfields underwear fame. Throughout his life he had enough money not to have to work for a living. He attended Dalhousie University and Harvard. During his student days he became a strong socialist. Although this affiliation faded, he remained very much a Red Tory.
After playing a role managing victory bonds during the Second World War, Stanfield entered Nova Scotia politics. The Conservative Party of Nova Scotia was in poor shape. The Liberals dominated the province, and the Conservatives did not have a single seat in the legislature. In 1948 Stanfield was elected leader of the party, and quickly began to revive it.
Stanfield served as premier of Nova Scotia, ruling as a moderate with a demonstrable social conscience. He won re-election numerous times with the help of the so-called Nova Scotia Mafia, a group of political advisors led by Dalton Camp and Flora MacDonald.
During his term as premier, Stanfield remarried, exchanging vows with Mary Hall in 1957.
In 1967 the federal Progressive Conservatives were racked by disunity between pro- and anti-Diefenbaker factions. Stanfield entered the race, and with the help of his Nova Scotian advisors he won a hard-fought battle on the fifth ballot.
In the federal election of 1968 a controversial photo of Stanfield fumbling a football catch at a political event became one of the defining images of his career, contrasting badly against the more vibrant and youthful image presented by Liberal leader Pierre Trudeau. To this day Canadian political commentators still point to this incident as one of Canada's foremost examples of "image politics", because this one photo was chosen for the front pages of newspapers across Canada even though many other photos of Stanfield catching the same football were also available.
Stanfield served as leader of the PCs and of Her Majesty's loyal opposition until 1976. He became reknowned as a gentlemanly and civil man, but after a string of election defeats this turned into a reputation for being unable to go for the jugular. He resigned and was succeeded by Joe Clark in 1976.
Mary Stanfield passed away of cancer in 1977, and the following year Stanfield married his third wife, Anne Austin.
After his retirement Stanfield stayed out of politics until the constitutional debates during Brian Mulroney's term as prime minister. Stanfield endorsed and campaigned for the Meech Lake Accord and the Charlottetown Accord, and both of these were supported in Nova Scotia, but they failed elsewhere.