[2] In 1974, Carrascalão founded the Timorese Democratic Union (UDT) with Domingos Oliveira, César Mouzinho, António Nascimento, Francisco Lopes da Cruz, and Jacinto dos Reis in the aftermath of the Carnation Revolution in Portugal.

[2][1] He and his brother, João Viegas Carrascalão, another member of the UDT, split following the Indonesian invasion of East Timor in 1975 and subsequent occupation of the country.

[1] He personally met with Xanana Gusmão in Lariguto in 1983 and in Ariana in 1990, which marked the beginning of dialogue between the resistance and Indonesian authorities.

Mário Viegas Carrascalão emerged as a key political figure in East Timor's transition from Indonesian occupation to full independence.

[4] In his resignation letter to Gusmão, Carrascalão lambasted the coalition government for failing to purchase construction supplies from a supplier he had recommended.

Carrascalão refused, writing, "At the age of 73, this is the first time anyone has ever called me stupid or a liar...My response is to resign from my position of deputy prime minister.

[2] President Taur Matan Ruak awarded the Collar of the Order of Timor-Leste, the nation's highest honor, in recognition of his service on May 18, 2017.

[2][1][5] Carrascalão died a day later at the Hospital Nacional Guido Valadares in Dili, East Timor, on May 19, 2017, a week after his 80th birthday.