Holmes was admitted to the Bar and admitted as a Solicitor of the Supreme Court of Queensland in 1982. In 1984 she was admitted as a Barrister of the Supreme Court of Queensland and was a Foundation Member of the Women's Legal Service in Queensland. She was a Crown Prosecutor in the Office of Commonwealth Director of Public Prosecutions from 1984 to 1986. In 1986 she began a law firm private practice focused on criminal and administrative law. She served as a Member of the Queensland Anti-Discrimination Tribunal from 1994 to 2000.