Supporting units

3 Commando Brigade not only consists of Royal Marines units, but also of combat support elements provided by other branches of the armed forces, mainly the Army. These include the Commando Logistic Regiment (consisting of both RM and Army personnel), 29 Commando Regiment Royal Artillery (based in Plymouth), and 59 Independent Commando Squadron Royal Engineers (based at Chivenor, near Barnstaple). These units provide the specialist artillery, combat service logistic, signals, and engineer support for the Brigade. All Army ranks serving with the brigade also undergo commando training on the All Arms Commando Course.

In practice in specific operations 3 Commando Brigade is configured to the task at hand with the attachment or detachment of units. For instance in the 1982 Falklands War two battalions of Parachute Regiment and a squadron of light tanks were attached to the brigade.