The World Player of the Year missed his country's recent friendlies against Greece and Mexico because of problems with his left knee and right thigh.
But the 29-year-old forward was cleared to make his return and start in the friendly against Ireland at New Jersey's MetLife Stadium.
Midfielder Raul Meireles, who has had a thigh problem, was also named in the team while central defender Pepe, who has been struggling with a leg muscle injury, was among the substitutes.
Ronaldo struggled with minor injuries during the closing weeks of Real Madrid's season and has not played since the Champions League final against Atletico Madrid, raising concerns about his fitness for the World Cup.
His timely return is a welcome boost for Portugal who are drawn in the same group as Germany, Ghana and the United States for the World Cup, which starts in Brazil on Thursday. (Reporting by Julian Linden; editing by Ken Ferris)
- Sports & Recreation
- Cristiano Ronaldo
- Raul Meireles