Born in 1926 in North Sydney, Nova Scotia.
Worked in administration for the Progressive Conservative Party for several years, prior to becoming involved in electoral politics.
First elected to the House of Commons in the 1972 general election as the Progressive Conservative Member of Parliament for the riding of Kingston and the Islands. She remained in parliament until her defeat in the 1988 election.
At the 1976 PC leadership convention, she became the first woman to mount a serious campaign for the leadership of one of Canada's two major governing parties. In this, she had been preceded by Rosemary Brown who ran in 1975 for the leadership of the New Democratic Party, and by Mary Walker-Sawka, who won two votes at the PC leadership convention in 1967.
When Joe Clark became Prime Minister of Canada in 1979, he made MacDonald the first female Secretary of State for External Affairs in Canadian history, and one of the first female foreign ministers anywhere in the world.
MacDonald returned to government after the PC victory in the 1984 federal election, serving first as Minister of Employment and Immigration, and then as Minister of Communications under Prime Minister Mulroney.
Since losing her seat in 1988, she has devoted her time to international humanitarian work.