When the PC Party took power as a result of the 1957 federal election, Prime Minister John Diefenbaker appointed her to the position of Secretary of State for Canada. In 1958, she became Minister of Citizenship and Immigration, and from 1962 until her defeat in 1963, she was Postmaster General. As Immigration Minister in 1962, Fairclough introduced new regulations that mostly eliminated racial discrimination in immigration policy. She also introduced a more liberal policy on refugees, and increased the number of immigrants allowed into Canada.