The principal functions of the Departments are as follows:-
- The Department of Defence deals with Integrated Defence Staff (IDS) and three services and various Inter-Service Organisations. It is also responsible for the Defence Budget, establishment matters, defence policy, matters relating to Parliament, defence cooperation with foreign countries and coordination of all activities
- The Department of Defence Production is headed by a Secretary and deals with matters pertaining to defence production, indigenization of imported stores, equipment and spares, planning and control of department production units of the Ordnance Factory Board and Defence Public Sector Undertakings (DPSUs.)
- The Department of Defence Research and Development is headed by a Secretary, who is also the Scientific Advisor to the Raksha Mantri(Defence Minister). Its function is to advise the Government on scientific aspects of the military equipment and logistics and the formulation of research, design and development plans for equipment used by the Services.
- The Department of Ex-Servicemen Welfare is headed by the Additional Secretary and deals with all resettlement, welfare and pensionary matters of Ex-Servicemen.
Integrated Defence Staff (IDS) was created on October 1, 2001, as a sequel to the decision by the Group of Ministers based on Kargil Committee Report. The staff of HQ IDS is provided from three Services, MEA, DRDO, Armed Forces HQ (AFHQ) Civil Services and DoD. IDS is presently functioning as staff in the advisory mode to the Chairman COSC and is headed by the Chief of Integrated Defence Staff to Chairman COSC (CISC)
The three Services Headquarters, viz., the Army Headquarters, the Naval Headquarters and the Air Headquarters functions under the Chief of the Army Staff (COAS), the Chief of Naval Staff (CNS) and the Chief of the Air Staff (CAS) respectively. They are assisted by their Principal Staff Officers (PSOs). The Inter-Services Organisations, under the Department of Defence is responsible for carrying out tasks related to common needs of the three Services such as medical care, public relations and personnel management of civilian staff in the Defence Headquarters.
A number of Committees dealing with defence related activities assist the Raksha Mantri(Defence Minister). The Chief of Staff Committee is a forum for the Service Chiefs to discuss matters having a bearing on the activities of the Services and to advise the Ministry. The position of Chairman of the Chiefs of Staff Committee devolves on the longest serving Chief of Staff and consequently rotates amongst the three services.
Finance Division in the Ministry of Defence deals with all matters having a financial implication. This Division is headed by Financial Advisor (Defence Services) and is fully integrated with the Ministry of Defence and performs an advisory role.