The first Spanish Constitution in modern history, the Constitution sanctioned in Cádiz in the year 1812 after important debates at the Constituent Assembly on the convenience or otherwise of having two chambers, set up a unicameral Parliament or Cortes, according with the Spanish traditional denomination.

- From 1834 to 1837

The Second Chamber - High Chamber - in Spain was brought forth by the 1834 Royal Statute, a kind of charter issued and Cortes summoning, in Ruling Queen María Cristina times, under the denomination of Estamento de Próceres, an aristocratical assembly composed of members either in their own rights or regally appointed, integrated by the nobility, Church hierarchies, High Administration representatives and the leading tax payers in the Kingdom.

Estamento de Próceres met during three Legislature terms from 1834 to 1836.

- From 1837 to 1845

Unicameral Constituent Cortes were summoned on August 21, 1836 to sanction the Constitution of 1837. This kept the bicameralism and, for the first time in Spanish Constitutional history, the High Chamber was renamed Senado(Senate).

The Senate, according with the Constitution of 1837, was a Chamber regally appointed from a list of three candidates filed by every province, having one Senator, minimum, each and the remainder until the total number was chosen according with the province population. It was required to be Spanish citizen, older than 40 years and having means of support.

Both chambers were invested same faculties in their quality as co-legislating bodies, with the exception of tax and public credit laws which were first filed at the Congress and on which this Chamber had the last word.

During the Constitution of 1837 term, the Senate met in ten Legislature terms, from 1837 to 1845.

- From 1845 to 1869

Bicameral Constituent Cortes were summoned on July 10, 1844, the Constitution of 1845 being then sanctioned. The Senate had at that Constitution a limited number of members all of them appointed by the King among personalities belonging to the Administration, the Army, the Church or those having been vested with a number of political charges and owning a given capital.

Both chambers were vested the same faculties, except as regards filing bills on taxes and public credit at the Congress.

During the Constitution of 1845 term, the Senate met twenty-one Legislature terms, from 1845 to 1868, with the interval of the bicameral Constituent Cortes summoned by Decree of August 11, 1854, to discuss and approve the Constitution of 1856 bill, a non nata Constitution since it was never published, foreseeing an elected Senate on a provincial basis. Thus, after elapsing the parenthesis from 1854 to 1856, the Constitution of 1845 was re-established with some alterations affecting the Senate in the sense that it reinforced the High Chamber conservative character including Senators who inherited their offices. Reformations entered in 1864 were abolished in 1857 and a further Senate composition alteration, somewhat more open than that of 1857, was passed in 1867.

On December 1868, after the so-called Glorious September Revolution of said year, unicameral Constituent Cortes were convened by Decree of December 6, 1868, that sanctioned the Constitution of 1869.

- From 1869 to 1873

The Constitution of 1869 maintained a bicameral system as well: Congreso de los Diputados and Senado, as equal co-legislative bodies having the same powers, with the exception of those cases established in the Constitution. The 1869 Senate was a partially renewable chamber in its fourth part every three years, or with full renovation in case of being regally dissolved. The elections were held through an indirect system on provincial basis; in every province, an Electoral Board composed by municipal electors was chosen by universal suffrage. This Board, by absolute majority, elected four Senators among a given number of categories (Congress Speaker or ex Speaker, Congressman having been elected in three general elections, High Bodies Chairmen, Commanders in Chief, Ambassadors, State Councillors, Supreme Court members, Archbishops or Bishops, University Rectors, Royal Academy Chairmen or Directors, Provincial Congressmen having been elected four times or Majors having been elected twice in towns having more than 30,000 souls, 50 leading taxpayers in the district or the 20 leading ones in the industrial or commercial subsidy of every province, etc.), providing they were Spanish nationals, older than 40 years and enjoying full use of their civil rights.

The Constitution of 1869 Senate met four Legislatures, from 1871 to 1873.

- From 1873 to 1876

Unicameral Constituent Cortes were summoned on March 11, 1873 to discuss a Constitution bill for the first Spanish federal character Republic. 1873 Bill maintained bicameralism, setting up a Senate having a clearly territorial composition, where Senators, at the rate of four per each State, would be elected by their relevant State Cortes. The Chamber would be fully renewed every two years. The Senate had no legislative initiative, being in charge of a singular function to warrant human personality's rights, powers from political bodies, Federation or Fundamental Code faculties, which implied a peculiar veto and reconduction to a Mixed Committee, in the first year, and with Executive-Senate veto having a composite character on the second year.

- From 1876 to 1923

Bicameral Constituent Cortes were summoned on December 31, 1875 (the Preparatory Board meeting to this end was held on February 14, 1876 and its Legislature Term closing decree took place on January 5, 1877) to draft the Constitution of 1876 that maintained the bicameral system with a Senate and a Congress having the same powers, in which the High Chamber was composed of 360 members, one half of them appointed by the King, by their own right and for life, and the other half being elected by the State corporations, with the largest taxpayers in the way determined by law. One half of the elective Senators -90 Senators- were renewed every five years, and all of them in case of dissolution of this part of the Senate by the King.

Senators by their own right were the King's and his Successor's sons, Spanish Grandees having an annual income of pesetas 60,000, Commanders in Chief, Patriarch of Indies and Archbishops, and Chairmen of the State bodies -Council of State, Supreme Court, etc.-. A condition to become Senator by royal appointment or by election by the State Corporations and larger taxpayers was to have been a Parliament Speaker, Congressmember in three different legislature terms, Minister, Bishop, Spanish Grandee, Ambassador, Lieutenant General, member of a High State Body, District Attorney, Chairman or Academician of a Royal Academy, Senator, large taxpayer, etc. It was required to be appointed Senator, in any case, to be Spanish national, older than 35 years, not having been sued or disqualified, and not having his assets placed under government control.

Throughout the Constitution of 1876, the Senate met in the following Legislature terms.

Senate was dissolved in 1923, during Primo de Rivera Dictatorship.

After the 1923-1930 term, unicameral Constituent Cortes summoned in May 1931; although in the Juridical Advisory Committee draft it was previewed a Senate having less powers than Congress, composed of five groups having fifty Senators each, the first one representing the provinces, second and third in behalf of worker and employer organizations, fourth by liberal professional Associations and fifth for Universities, cultural institutions and religious confessions, the Constitution of 1931 was inclined to a unicameral system in which legislative power was performed through the Cortes or Congreso de los Diputados.

During Franco's period there was no Senate.