Austin Parnell was admitted to practice as a Barrister and Solicitor in Victoria on 2 April 1964 and in New South Wales as a Solicitor on 1 November 1985. He was a member of the Victorian Crown Solicitor's Office for seven years engaged in principally litigious work at a high level and when he left in May 1969 was Legal Assistant to the Chief Commissioner of Police.

He joined Oswald Burt & Co. in May 1969 and became a partner the following year engaged principally in litigation. He subsequently became a partner at Middletons Oswald Burt and Westgarth Middletons.

He first signed the Bar Roll in 1990 and practised principally in the area of Professional Misconduct. He remained until 1997 and subsequently practised as a Solicitor principally in New South Wales until rejoining the Bar in May 2009.