On 1 June 2018, the PSOE called a vote of no confidence against Prime Minister Mariano Rajoy, successfully passing the motion after winning the support of Unidas Podemos, as well as various regionalist and nationalist parties.

His mother also worked as a civil servant, in the social security system, and later studied to become a lawyer, ultimately graduating alongside her son at the same university.

He subsequently enrolled at the UCJC to study a Doctorate in Economics, earning his PHD 18 months later by writing a dissertation entitled Innovaciones de la diplomacia económica española: Análisis del sector público (2000–2012) (English translation: Innovations of Spanish Economic Diplomacy: Analysis of the Public Sector (2000–2012)), supervised by María Isabel Cepeda González.

[26] In January 2013, Sánchez returned to Congress representing Madrid, replacing Cristina Narbona, who resigned to accept appointment at the Nuclear Safety Council.

After the resignation of PSOE leader Alfredo Pérez Rubalcaba, following poor results at the 2014 European Parliament election, Sánchez launched his campaign to succeed him on 12 June 2014.

[12] Presenting a platform based on political regeneration, Sánchez called for constitutional reforms establishing federalism as the form of administrative organisation of Spain to ensure that Catalonia would remain within the country; a new progressive fiscal policy; extending the welfare state to all citizens; increasing the membership of labour unions to strengthen economic recovery; and regaining the confidence of former Socialist voters disenchanted by the measures taken by Zapatero during his term as prime minister amid an economic crisis.

Following the 2016 general election, Sánchez argued the PSOE should refuse to allow the PP to form a government, which would break the national political deadlock.

Susana Díaz, the President of Andalusia, began to lead criticism of Sánchez's leadership, arguing that his hardline position on government formation was harming the party.

The situation quickly developed into a party crisis, dubbed by some in the media as the "war of the roses", after Sánchez called a special PSOE congress for the autumn to settle the issue.

[33] Soon after his resignation, the PSOE caretaker committee decided to abstain in the investiture vote, which would enable the PP's Mariano Rajoy to be re-elected as prime minister.

Saying that he could not obey this directive as it would mean "betraying his word" not to allow Rajoy to be re-elected, Sánchez resigned his seat in the Congress of Deputies, and declared he would stand in the upcoming leadership election.

[36] After resigning as Secretary-General and from the Congress, Sánchez began a national tour, driving his own car around to visit party members throughout different parts of Spain.

[37][38] After an energetic campaign, during which he criticised the caretaker committee for allowing the investiture of Rajoy, on Sunday, 21 May 2017, Sánchez was re-elected Secretary-General by the party membership, taking 50.2% of the vote, and defeating his rival Susana Díaz, who took 39.94%, as well as Patxi López, who won 9.85%; his position was affirmed at a PSOE executive meeting on 17 June, and the following day he was confirmed as Leader of the Opposition, despite no longer holding a seat in the Congress.

[43] Outlining his priorities, Sánchez said he would form a short-term government that would increase unemployment benefit and propose a law guaranteeing equal pay between the sexes, before dissolving the Congress of Deputies and holding a general election.

[49] On 24 August the Cabinet approved a decree modifying two aspects of the 2007 Historical Memory Law to allow for the exhumation of Franco's remains from the Valley of the Fallen.

[51] Sánchez would, however, eventually grant a partial pardon to most convicts in 2021,[52] stressing that despite the pardon there would never be a referendum for the independence of Catalonia,[53] with then Spokesperson María Jesús Montero that "We will not renounce, as a government, to do what we think is best for our country, its coexistence, stability and progress" and the Catalan conflict needs "that the word, dialogue, coexistence and the capacity for reunion take on a leading role that should never have been lost".

[57] On 16 January 2019, in a speech before the European Parliament, he said that the EU should be protected and turned into a global actor, and that a more social Europe is needed, with a strong monetary union.

Overruling Robles, Sánchez ordered the sale to proceed, allegedly due to a promise made to Susana Díaz to help protect jobs in the shipyards of the Bay of Cádiz, highly dependent on the €1.813 billion contract with Saudi Arabia to deliver five corvettes.

[68] Following the fall of Kabul and the subsequent de facto creation of the Islamic Emirate of Afghanistan, the Prime Minister offered Spain as a hub for Afghans who collaborated with the European Union, who would later be settled in various countries.

Von der Leyen praised the Sánchez Government's initiative, stating that the actions of Spain represented "a good example of the European soul at its best".

[81][82] After the Congress of Deputies formally rejected Feijóo's bid to be invested in September 2023, King Felipe VI appointed Sánchez to form a government.

[83] After obtaining the support of the left-wing Sumar alliance, as well as a series of pro-independence and regionalist political parties, the Congress of Deputies re-elected Sánchez as Prime Minister on 16 November 2023; he was formally appointed to a third term the following day, sparking protests.

"[94] On 24 April 2024, due to a court investigation of his wife, Begoña Gómez, for alleged influence peddling charges presented by Manos Limpias, a far-right proxy trade union,[95][96][97][98] Sánchez announced through a letter in the X social network that he was considering his resignation from the position of prime minister, citing a right-wing media offensive to wear him down.

[99][100][101] Several media noted how Manos Limpias' charges against Sánchez's wife were based on press headlines and fake news,[102][103] a fact that the trade union acknowledged as possible.

[104] On 26 April 2024 and in a joint investigation, elDiario.es, El País and La Vanguardia newspapers revealed a plot by the PP, dating back to Mariano Rajoy's government in 2014, to spy and produce information on Sánchez's and Gómez's relatives to "politically kill him" by using Manos Limpias to present criminal charges.

[117] Sánchez replied by accusing opposition leaders Alberto Núñez Feijóo and Santiago Abascal of trying to influence the outcome of the European Parliament elections on 9 June by using his wife's situation against him, while claiming that the unwritten rule of not issuing judicial resolutions that could affect the normal development of an electoral campaign and the vote had not been followed this time.

[120][121] On 15 July 2024, businessman Juan Carlos Barrabés testified and stated that Begoña Gómez had met with him up to eight times at the Palace of Moncloa, the prime minister's official residence and workplace.

[132] Sánchez tried to push through a law that would introduce mandatory distribution of migrants among Spanish regions in order to alleviate pressure in the Canary Islands.

Until the transition to democracy following the death of Francisco Franco in the mid-1970s, foreign languages were not widely taught in Spanish schools, and former Prime Ministers, as representatives of their generation, have been known for struggling with them as a result.