O'Halloran was born in Burnie, Tasmania, and educated at Smithton High School and Devonport Community College. She worked as an education officer and child care director for Circular Head Council, before moving to Darwin, Northern Territory in 1989 where she studied for a Bachelor of Children's Services at Charles Darwin University. In 1993, she joined Somerville Community Services, as deputy CEO and manager, and became CEO in 1998.
In 2014, O'Halloran was made a Member of the Order of Australia for significant service to people with a disability through roles with a range of organisations, and to the community. She was subsequently advanced to Officer of the Order of Australia in the 2019 Queen's Birthday Honours for distinguished service to the people of the Northern Territory, and to the disability sector through a range of executive roles.
- "New NT Administrator appointed". NT News. 31 August 2017. Retrieved 30 October 2017.
- Who's Who in Australia 2017, ConnectWeb, 2017.
- "O'HALLORAN, Vicki Susan". Australian Honours. Department of Prime Minister and Cabinet. Retrieved 30 October 2017.
- "O'HALLORAN, Vicki Susan". Australian Honours. Department of Prime Minister and Cabinet. Retrieved 10 June 2019.
| Administrator of the Northern Territory