He can declare war or conclude peace with authorization of the Cortes Generales, provided this act is countersigned by the Prime Minister.

Beneath the Ministry of Defense are five subordinate principal departments: the Armed Forces headed by the Chief of the Defence Staff (JEMAD) which is divided in three military branches led by the Chief of Staff of the Army (JEME), the Chief of Staff of the Navy (AJEMA) and the Chief of Staff of the Air Force (JEMA); the Secretariat of State for Defence (headed by the Secretary of State, SEDEF); the Undersecretariat of Defence headed by the Ministry's Under-Secretary (SUBDEF) and the General Secretariat for Defence Policy head by the Secretary-General (SEGENPOL).

It subsists until the loss of those imperial provinces and is definitively suppressed by Royal Decree of 15 April 1899.

The Monarch remained as the symbolic commander-in-chief and the position of Secretary of State for Defence was created too.

[9] In 2018, the National Intelligence Centre returned to the department's structure,[10] and Paz Esteban López was appointed its first female director in 2020.

[12] The Department is organized as follows:[3] The Civil Guard depends on the Ministry of Defence in the terms stipulated by laws.

The Government is the body in charge of establishing the defense policy as well as control of the military administration.

The Chief of the Defence Staff (JEMAD) is the fourth military authority, in charge over the operative command of the Armed Forces.

The Ministry of War installed in the Buenavista Palace in 1847, a building that previously housed some military facilities.

Already during the democratic transition, in 1977 the new Ministry of Defense was created, being headquartered in the Palacio de Buenavista until 1981.