Walker was admitted to the NSW bar in 1979. He was appointed Senior Counsel in 1993. He was president of the NSW Bar Association from November 2001 to November 2003, and had been Vice-President from 1996 to 2001. He was President of the Law Council of Australia from 1997 to 1998.
Walker is a member of the Council of Law Reporting for New South Wales, and has been Editor of the NSW Law Reports since 2006. He is a patron of the State Library of NSW as a Foundation Senior Fellow and has been a Member of the NSW Health Clinical Ethics Advisory Panel since 2003. He was Governor of the Law Foundation of NSW from 1996 to 2007, and Special Commissioner of Inquiry for the NSW Government into Sydney Ferries in 2007. Walker has been a director on the board of the Sydney Writers' Festival since 2000. He was a Foundation Member and has been Director of the Australian Academy of Law since 2007.
In April 2011 Bret Walker was appointed as the Independent National Security Legislation Monitor
- Find a Barrister, NSW Bar Association
- Who's Who Australia – entry for Bret William Walker
- Bar News, Summer 2001/2002, p. 2.
- Bar News, Summer 2003/2004, p. 2.
- , Our Presidents, Law Council of Australia
- See glass placard at Macquarie St entrance to the State Library of NSW, or see also: 
- Sydney Writers' Festival website – Board Members
- Australian Academy of Law
- The Red Room Company Website