Brian Simpson joined the Edmonton Police Service in May of 2012. Deputy Chief Simpson was considering law school at the onset of his working life, but quickly realized that was not his passion. Instead, he completed a Bachelors degree in Criminology at Simon Fraser University before pursuing a career in policing. When it was time to put in requests for deployment, he requested Grande Prairie, as it was the busiest RCMP detachment in Alberta. Deputy Chief Simpson stayed in Grande Prairie for seven years and then accepted a role in Calgary as an Investigator. He worked in Calgary for nine years in General Investigation, Major Crimes (Homicide) and the Commercial Crime divisions.

In 1996, Deputy Chief Simpson accepted a supervisor role as Operations Sergeant in Wetaskiwin. He was in this role for a short six months when the Staff Sergeant became ill, and Deputy Chief Simpson became the Acting Detachment Commander Staff Sergeant. Through a candidate selection board, he was made an Officer in charge of Hobbema and Wetaskiwin.

Deputy Chief Simpson was the Officer in Charge of Federal Drug Enforcement (responsible for Edmonton, Calgary and Red Deer) for a little over a year. In 2004, he was asked to work in Client Services-Administrative, a new role that was being tested. A year later, he competed for the Officer in Charge of the City of Red Deer position and was successful, remaining in the role for just over five years. In September 2011, Deputy Chief Simpson accepted the Director General of Operational Readiness and Response at RCMP Headquarters. From 2001 to 2011, Simpson was the Incident Commander for the RCMP ERT Team

Deputy Chief Simpson was a Gold Commander at the 2010 Winter Olympic Games in Vancouver, and the Unified Command Centre Commander for the G8/G20 Conference in Barrie, Ontario.