The Napa Special Investigations Bureau was formally established on March 1, 1976, through a state grant funded by the California Office of Criminal Justice Planning. In 1979, the grant funding had expired; however, Napa County and the Cities of Napa, St. Helena, and Calistoga opted to maintain the funding for NSIB, to continue narcotics investigation and enforcement efforts. 

NSIB continued to operate under the direction of a NSIB Governing Board comprised of the chief law enforcement administrators of participating law enforcement agencies. The agencies were the Napa County District Attorney’s Office, the Napa Sheriff’s Department, Napa Police Department, St. Helena Police Department, Calistoga Police Department, the California Highway Patrol, and the Napa County Probation Department.

In 1988, the NSIB Governing Board and the California Department of Justice, Bureau of Narcotic Enforcement, entered into a Memorandum of Understanding, an inter-agency agreement where, under the general administrative control of the NSIB Governing Board, BNE would assign a Special Agent Supervisor to assume the direct management of NSIB. As a result of the agreement, NSIB became one of 50 other county narcotic task forces participating in the BNE’s Statewide Regional Task Force program. 

In January 2000, the NSIB Governing Board unanimously agreed to include the Napa County Probation Department as a member of NSIB.

Under the task force program, BNE and NSIB combined their respective efforts and resources primarily to conduct criminal investigations and enforcement activities aimed at combating the illegal manufacturing, trafficking, and use of controlled substances throughout Napa County. The alignment between NSIB and BNE also provided the task force with statewide linkage to BNE regional offices, regional task forces, Department of Justice training programs, and Department of Justice investigative, intelligence, and analytical services.

In July 2011, the State of California de-funded BNE causing it to be abolished.  The NSIB governing board chose to continue NSIB's public safety efforts by taking local command of the program.  NSIB is now managed by a Lieutenant from one of the participating agencies.

In January 2014, the California Highway Patrol (CHP) assigned an investigator to NSIB.  At the same time NSIB formally expanded its mission to provide assistance to participating agencies with investigative support related to major crimes.

In 2016, NSIB included commercial sex trafficking as an investigative point of focus.