The right back was on Tuesday named in a 26-man squad for the African Nations Cup in Gabon.
Dabo played for Portugal at the U-20 World Cup in Turkey in 2013 but will now seek to change his footballing nationality to play for the west Africans as they make their Nations Cup debut, competing in the opening game of the 2017 finals against hosts Gabon in Libreville on January 17.
Bissau-born Dabo will have to apply to FIFA to make the change, a process that can be hurried in order for him to compete at the tournament in Gabon.
The 23-year-old from Arouca, who began his career at Braga, was not named by coach Baciro Cande when he released a preliminary squad of 35 earlier this month.
That list featured just three just three goalkeepers, which meant, in theory, all would be going to the tournament.
But that has changed with uncapped Edouard Mendy from French Ligue 2 club Stade Reims being replaced by Rui Dabo, who is at Cova da Piedade, who sit fourth in the second flight of Portuguese football.
Cande has picked a squad entirely made up of players based in Europe, including some without clubs.
But he has dropped plans to persuade other ex-Portuguese junior internationals Yazalde from Rio Ave and Judilson Mamadu Tuncará Gomes, otherwise known as Pele, to play for the team.
The 26-man squad will have to be trimmed by three for the finals.
Goalkeepers: Rui Dabo (Cova da Piedade, Portugal), Papa Masse Mbaye Fall (CD Orellana Costa Dulce, Spain), Jonas Mendes (Salgueiros, Portugal)
Defenders: Mamadu Cande (Tondela, Portugal), Tomas Dabo (Arouca, Portugal), Eridson (Freamunde, Portugal), Emmanuel Mendy (unattached), Rudinilson Silva (unattached), Agostinho Soares (Sporting Covilha, Portugal), Juary Soares (Mafra, Portugal)
Midfielders: Abudu (Operário Lagoa, Portugal), Bocundji Cá (unattached), Idrissa Camara (Avellino, Italy), Francisco Júnior (Stromsgodset, Norway), Jean Paul Mendy (US Quevilly-Rouen, France), Naní (Felgueiras, Portugal), Sana (Academica Viseu, Portugal), Toni Silva (Levadiakos, Greece), Zezinho (Levadiakos, Greece)
Strikers: Aldair (Olhanense, Portugal), Abel Camara (Belenenses, Portugal), João Mário (Chaves, Portugal), Fredric Mendy (Ulsan Hyundai, South Korea), Piqueti (Sporting Braga B, Portugal), Sami (Akhisar, Turkey), Ze Turbo (Tondela, Portugal).