Her first library job was at Mosman Public Library in Sydney. Moving a few years later to Western Australia, Pat Gallaher worked in public libraries in regional areas for almost 30 years. She held positions in Paraburdoo and Karratha, and then for 20 years as the regional librarian for the City of Geraldton (1981-2001). While at Geraldton Library Pat introduced many new services and developments, including a Service to house-bound residents, the internet, and an automated library management system. Pat also oversaw extensions to the Library and established the local studies collection.

Recognizing a need to foster young Writers, Pat initiated the Randolph Stow Young Writers Award in 1989 to encourage school students in the Geraldton region of Western Australia to write. Pat Gallaher served on many committees promoting regional arts, including the Geraldton Arts Council and as a board member of Country Arts WA. In 1987 Pat formed the Mid West regional chapter of the Australian Library and Information Association (ALIA).

Following her retirement from the Geraldton Library, Pat was elected to the Geraldton City Council, serving on the municipal council from 2001-2003.

Pat Gallaher joined the Library Board of Western Australia in 2002 as the representative for the Western Australian Local Government Association and served a four-year term to 2006. She was named as a Fellow of the Library Board in 2011, in recognition for her commitment to libraries and the arts in regional Western Australia. She was interviewed on 28 October 2013 as part of the Library Board of Western Australia 60th anniversary project.

Pat Gallaher died in Perth, Western Australia on 11 December 2014.