Prior to the birth of the Philippine National Police, the legal arm of the defunct PC/INP was the Office of the Constabulary Judge Advocate. On January 2, 1992, upon the effectivity of Republic Act No. 6975, the Constabulary Judge Advocate Office was renamed as Police Legal Advocate Service. In 1992, it was merged with the Inspector General leading to the creation of the Internal Affairs Division. When the Internal Affairs Division was deactivated, the PNP Legal Service emerged on October 21, 1992 pursuant to Staff Memorandum No. 14, GHQ, PNP.
The PNP Legal Service was created as an additional Administrative support unit via NAPOLCOM Resolution No. 93-023 dated May 27, 1993.
It is currently operating as a reorganized unit pursuant to NHQ-PNP General Orders Number DPL-10-09 which was approved by the NAPOLCOM through Resolution Number 2011-321 dated September 13, 2011.