There were question marks about the 38-year-old forward’s international future following the 2022 World Cup.
Roberto Martinez has since replaced Fernando Santos as the team’s manager and picked Ronaldo in his first squad.
Martinez said Ronaldo “is very important for the team” and “I do not look at the age”.
Portugal host Liechtenstein on 23 March and are away to Luxembourg three days later.
Ronaldo, who has scored a men’s record 118 goals in 196 appearances for Portugal, left Manchester United in November following a controversial interview in which he criticised the club before joining Saudi Arabian side Al Nassr on a free transfer in January.
He has scored eight goals in nine appearances for Al Nassr.