Support Battalion is the backbone of the regiment. The Battalion 's duties diversify across the board. Instructional Training Company provides the recruit training battalions with martial arts, water survival, and academic instruction. Receiving Company's duties takes care of incoming civilians and process them to become recruits. They also handle recruits that are pending separation from MCRD. Special Training Company has the responsibility of rehabilitating injured recruits ; they provide physical conditioning to recruits not meeting the minimum standard, and responsible for any recruits that are on medical hold pending treatment. Headquarters company is comprised of Basic Marine Platoon and the administration and training shops to support the rest of the companies.

Support Battalion is led by Lieutenant Colonel Arthur L. Graham III and Sergeant Major Eric D. Ramirez. Support Battalion is organized into four companies:  Headquarters Company, Special Training Company, Instructional Training Company, and Receiving Company to support the process and training of recruits aboard Marine Corps Recruit Depot San Diego.