Nancy Hollister first entered public office when she was elected to the Marietta City Council in 1980. Hollister would serve on city council until being elected Mayor of Marietta in 1984. As Mayor, Hollister worked to attract new businesses to the area, promote tourism, and secured funding for a new bridge across the Ohio River.

Hollister was elected Ohio's 60th Lieutenant Governor in 1994 to replace incumbent lieutenant governor Mike DeWine, who was elected to the U.S. Senate. Hollister would oversee several State and Local Government Commissions. These included the Governor's Office of Appalachia, the Governor's Workforce Development Board, the Ohio Department of Agriculture, the Ohio Bureau of Employment Services, the Ohio School-to-Work Initiative, the Office of Housing and Community Partnership, the Ohio Coal Development Office, and the Ohio Farmland Preservation Task Force.

Voinovich resigned as governor on December 31, 1998, and with that, Hollister became governor. Hollister became Ohio's first and to date only female governor. She only served 11 days in office, making her Ohio's shortest-serving governor, as she was essentially finishing out Voinovich's term. She was succeeded by Bob Taft, who was elected governor during the same election cycle, but whose term didn't officially begin until January 11, 1999.

Upon leaving the Governor's office, Hollister was appointed to the Ohio House of Representatives, representing the 93rd district, in 1999. She ran for and was elected to the seat in 2000 and 2002. In her final run for office to date, Hollister was defeated by Jennifer Garrison in 2004.

A key issue in the campaign was Hollister's opposition to a constitutional amendment to ban same-sex marriage. Garrison – the Democrat – ran to the ideological right of Hollister on the same-sex marriage ban which passed during the same 2004 election 61.71% to 38.29%.

In May 2016, she was appointed by Gov. John Kasich to fill a vacancy on the state Board of Education.