In 1984 he got a law degree from the Portuguese Catholic University, where he met Manuel Monteiro who, 10 years later, would serve as Portas's stepping stone into the CDS-PP and national politics.

In his mid-teens (1974–75) he began contributing to the official newspaper of the youth wing of the PSD (which at the time was called Partido Popular Democrático, 'PPD').

He first became nationally known at 15 years of age when he wrote a letter-to-the-editor of the daily evening newspaper Jornal Novo that prominently published it under the heading "Three Betrayals" ("Três Traições") directly accusing then president Ramalho Eanes, prime minister Mário Soares and foreign minister Diogo Freitas do Amaral of "selling out" Portugal's African colonies in 1974–75.

[6] In 1987, he co-founded, with Miguel Esteves Cardoso, the weekly newspaper O Independente, which started publication in May 1988 and became known for its innovative editorial concepts as well as for denouncing political scandals, often on the basis of little more than hearsay.

He was a sporadic panel member in a popular weekly night TV talk show (Raios e Coriscos) and in the Portuguese edition of Crossfire.

He would later profess to have been a staunch follower of PPD's founder Francisco Sá Carneiro, who is said to have relished the views of the 14-year-old Paulo Portas and personally sponsored his full PSD membership in 1978.

Sá Carneiro died in 1980 and, following a bitter loss in an internal election of the party's youth-wing JSD, Portas quietly left PSD in 1982.

[13] In 1995, Portas formally joined the CDS-PP with the full support of Manuel Monteiro, who put him at the top of the party list in the district of Aveiro thus ensuring that he would become a member of the Portuguese Parliament in that year's legislative elections.

[21] Later, Marcelo Rebelo de Sousa, in 1999 when he was leader of Portugal's Social Democratic Party (PSD), sought an elections alliance with Paulo Portas's CDS-PP that was initially agreed but collapsed shortly.

As Minister of Defense, Paulo Portas was also determinant in aligning Portugal with George W. Bush's 2003 Iraq invasion by saying he had personally "seen irrefutable evidence of weapons of mass destruction" while on an official visit to Washington.

[27] In the 2005 early elections, the two incumbent coalition parties suffered a crushing defeat, with CDS-PP losing 60,000 votes and two of its fourteen seats in Parliament.

[38] By focusing on his duties as Minister of Foreign Affairs, he also managed to distance himself from the difficult decisions related to Portugal's economic austerity program.

More than once he kept silent or expressed his disagreement with unpopular measures taken by the government to which he belonged,[39] and on 2 July 2013 he abruptly resigned in protest at the appointment of a Finance Minister (Maria Luís Albuquerque) he did not approve of, a decision he called "irrevocable" but that he subsequently revoked.

In control of the key ministries of Economics, Agriculture, Labor and Social Security (held by his CDS-PP ministers), Paulo Portas came to wield political power far beyond the 12% of the national vote his party received in the 2011 elections.

[42] As part of his Deputy Prime-Minister attributions, Paulo Portas took charge of the negotiations on Portugal's IMF/EC/ECB-supported program, the terms of which he had publicly declared to be against.

Having ceased his functions as Deputy Prime-Minister on 26 November 2015, Paulo Portas presented himself in Parliament the following day to take up the position for which he had been elected on 4 October by the Lisbon electoral district.

[46] Accordingly, on 13 March 2016, Paulo Portas stepped down in acclaim at a special convention of his CDS-PP party where he was replaced by his longtime protégée and former government colleague Assunção Cristas.

[52] Paulo Portas then went ahead with the purchase of twelve EH101 helicopters from manufacturer AgustaWestland at a total cost of 300 million euros for Portugal.

"[59] Portas is a lifelong bachelor, who has never publicly assumed a romantic relationship and who invariably attends his many official functions unescorted or in the casual company of socialite women known to be attached to other men.

"[60] Portas is known to be a fan of Parov Stelar, a well-known Electro swing musician,[61] and a supporter of Lisbon football team Sporting Clube de Portugal.