[4] Rebelo de Sousa has previously served as a government minister, parliamentarian in the Assembly of the Portuguese Republic, legal scholar, journalist, political analyst, law professor, and pundit.

[5] He is named after Marcelo Caetano, the last prime minister of the Estado Novo regime and a friend of his father.

[23] In December 2020, Marcelo Rebelo de Sousa announced his intention to run for office again in the 2021 Portuguese presidential election.

[25] During his presidency, Rebelo de Sousa has publicly supported making restitution and acknowledging abuses made during Portugal's colonialist history and the country's role in the Atlantic slave trade.

[34] In December 2017, Marcelo Rebelo de Sousa underwent emergency surgery at Curry Cabral Hospital in order to treat an incarcerated umbilical hernia.

[38] In June 2018, Marcelo Rebelo de Sousa was briefly hospitalized after he collapsed after a visit to Bom Jesus do Monte sanctuary in Braga; the incident was caused by a sudden drop in blood pressure alongside acute gastroenteritis.

[39][40] In October 2019, he underwent planned cardiac catheterization at Santa Cruz Hospital, Carnaxide, in the outskirts of Lisbon, after accumulated calcium was detected in one of his coronary arteries.

[41] On 8 March 2020, Marcelo Rebelo de Sousa suspended all his public agenda and returned to his private home in Cascais, entering a voluntary quarantine period for 14 days after being revealed that a group of students from Felgueiras, who had visited Belém Palace some days before, had also been quarantined after a positive case of COVID-19 was detected in their school.

[52] On 5 July 2023, Marcelo Rebelo de Sousa collapsed during a visit to the NOVA University School of Science and Technology, in Almada.

His chief of staff, Fernando Frutuoso de Melo, assured the situation was probably due to the heat and to the President's "heavy schedule".

After being submitted to several medical exams, the President was discharged four hours later, with a Holter monitor, and addressed journalists on his way out from the hospital, saying he had had an episode of low blood pressure since he had skipped lunch — as he usually does, replacing it with Fortimel, a medical nutrition supplement — and had been offered a glass of warm moscatel shortly before he fainted that "must have upset, probably, [his] digestion".

In the following years, Sousa and Mota Veiga had two children: The couple separated in 1980 and divorced in 1983,[2] although Marcelo, citing his Roman Catholic faith, believes marriage lasts until death.

[58] He started dating his former student Rita Amaral Cabral in 1981, who at the time was his fellow lecturer at the Faculty of Law of the University of Lisbon.

[60] In 2023, President of Portugal Marcelo Rebelo de Sousa became embroiled in a controversy following a TVI program that suggested he had intervened to expedite treatment for Brazilian twins with Zolgensma, a rare and highly expensive drug administered in a single dose costing two million euros.