Before entering politics, Shipley was involved with several community organizations.
Shipley was elected to the New Zealand Parliament in the 1987 election. She won the Ashburton electorate.
When the National Party returned to power in 1990, Shipley was appointed to the Cabinet of New Zealand under Jim Bolger. She was the Minister of Social Welfare (1990-1996), the Minister for Women's Affairs (1990-1996), a member of the Minister of Health (1993-1996) and a member of the Minister of Transport (1996-1997).
In December 1997, after Bolger resigned as Prime Minister, Shipley was elected as his replacement unopposed.