After the Carnation Revolution in 1974 and the independence of the territory as the People's Republic of Angola, he returned with his family to Europe and settled in Vila Real, in northern Portugal.

He started very early in politics, as a 14-year-old boy, and had a long and prominent career in the youth branch of the Social Democratic Party (PSD), the JSD, where he was a member of the National Council (1980–1982).

As a young student, his academic interests, vocations and ambitions were directed towards a future career in medicine, to follow his father and older sister's steps, or instead mathematics.

Then, after the Carnation Revolution in 1974, and the dismantling of the Portuguese Overseas Empire in Africa, he returned to Europe, settling in his grandparents estate, in Vale de Nogueiras, near the city of Vila Real, Norte Region, Portugal.

[8] He worked for the youth branch of the PSD party preparing motions and documents, and these time-consuming tasks impacted his final high school grades.

He did not, however, finish his degree, having instead elected to work full-time in his party's youth branch – his new life in the capital city of Portugal having probably been a driving factor in this decision.

By 2010, in a context of sovereign default, he helped defeat the Socialist government under the leadership of José Sócrates when it tried to adopt a package of austerity measures to maintain economic stability, leading to the resignation of the prime minister on 23 March 2011, and the general election of 5 June 2011.

Passos Coelho's political program was considered by the Portuguese left (Socialist Party (PS) and its communist political allies), which had governed the country during most of the time until the financial collapse of 2010, as strictly aligned with economic liberalism,[18][better source needed] and included a firm intention to accomplish the European Union/IMF-led rescue plan for Portugal's sovereign debt crisis.

[25] It was not certain if he would try to overrule the previous José Sócrates-led Socialist government laws that allowed abortion until 10 weeks and same-sex marriage in Portugal.

[27] Other creations of the previous cabinets led by former Prime Minister José Sócrates were criticized by Passos Coelho, including the state-sponsored Novas Oportunidades educational qualification program for unschooled adults, which was dubbed a fraud due to alleged low standards of intellectual rigor and academic integrity.

Nevertheless, due to Portugal's legal constraints[34] avoiding planned job cuts like those made across several developed countries at the time to fight overspending and overstaffing at municipality level,[35][36][37][38] the 2013 mergers eventually increased the spending with the parishes.

[39] The Portuguese Constitutional Court, with the praise of most unions and opposition party leaders, eventually rejected the equivalent to 20% of the government austerity policies proposed by Passos Coelho and his cabinet.

[51] He continued leading the PSD in opposition until a poor performance in the 2017 Portuguese local elections prompted him to announce his resignation that would take place once a new leader was selected in December.

After an inaugural speech in which he promised, in the long run, to stabilize the economy, promote financial growth, employment and protect the ones who needed the most, he moved on to adopt deep austerity measures that, on the view of his detractors, within the first year of government, led to the exact opposite.

[53] In addition, his government had earlier adopted a promoting stance on emigration, often advising the growing number of young unemployed people to leave the country.

[42] On 15 September 2012, Passos Coelho and his coalition government faced one of the biggest civil protests in the history of Portuguese democracy, where demands were made for solutions to be put in place.

On 21 September 2012, while the Prime Minister and members of the cabinet were meeting with President Aníbal Cavaco Silva, a large number of citizens protested in front of the presidential house, the Belém Palace, some throwing bottles at security forces.