The three women, who all trace their origins to Guinea-Bissau, an impoverished former Portuguese colony in west Africa, won office in the October 6 general election when Prime Minister Antonio Costa's Socialists were re-elected but without an absolute majority.
A total of 89 women were elected -- an unprecedented number in the 230-seat parliament -- following a new gender parity law requiring that 40 percent of elected lawmakers are female.
Portugal has a significant minority population from its former African colonies in Angola, Mozambique, Sao Tome and Principe, Guinea Bissau, and Cape Verde as well as Brazil.
Campaigners complain of discrimination in areas ranging from education to housing, employment to the justice system and of a shortage of black faces in business, the media and politics, although progress has been made in recent years.
After taking office in 2015, Costa, who is of Indian descent, nominated Portugal's first black cabinet minister, appointing Francisca Van Dunem, who was born in Angola, as justice minister.
She is keeping the post in Costa's new cabinet which will be sworn in on Saturday.
The best known of the newcomers is Joacine Katar Moreira, 37, an anti-racism activist who moved to Portugal from Guinea-Bissau when she was just eight and headed a list of upstart eco-socialist party LIVRE, or "FREE", winning the new formation's first and only seat in parliament.
The others are Romualda Fernandes, a 65-year-old lawyer and migration expert who won a seat representing the Socialists and Beatriz Gomes Dias, 48, the president of anti-racism association Djass, who ran with the far-left Left Bloc party.
Djass has proposed a memorial honouring the millions of African slaves which Portuguese ships transported to the Americas. The project has become a lightning rod for debate about the country's colonial past.
Up until now the only black person to serve as a member of parliament since Portugal returned to democracy in 1974 was a man -- Helder Amaral who represented the conservative CDS party between 2002 and 2019.
Moreira, who became a Portuguese national in 2003, vowed during her victory speech to become the voice of "anti-racism" and "leftwing radical feminism" in parliament.
Thousands of people have signed an online petition demanding that she not be allowed to take up her seat because at her victory celebration, several people were seen waving flags from Guinea-Bissau instead of Portugal.
"This has always been a war for people like me," Moreira tweeted in response to the petition.