After being educated in Canberra, Gallagher obtained her BA from Australian National University. She was a project worker for the Woden Community Service and from 1994-1997 worked for People First ACT, an organisation providing advocacy and support to individuals with an intellectual disability. She has been active in the community and union sectors for over ten years. She has advocated for both adult and children with intellectual disabilities and for the industrial interests of workers as a Community and Public Sector Union national organiser.

Sources used to compile this entry: 'Katy Gallagher, MLA', in ACT Labor, http://www.actlabor.com.au/people/KatyGallagher.html.