The Real Madrid striker, who missed his country's previous two warm-up games because of thigh and knee injuries, was not at his brilliant best for long periods of a one-sided friendly in the United States yesterday. (Agencies)
But coach Paulo Bento will just be relieved to see his captain and talisman back after an injury layoff that had sparked fears that Ronaldo might not be fit for Brazil.
Ronaldo was substituted on 65 minutes, but it appeared to have been a planned change and there was no indication that he was suffering any ill effects from his injury problems.
He was replaced by Real teammate Pepe, a key defender and another whose World Cup preparations have been badly hindered by injury.
Portugal, who were to fly to Brazil immediately after the match, start their World Cup assault against Germany on June 16 in Group G -- the so-called "Group of Death" -- which also includes the USA and Ghana.
It took Ronaldo just 51 seconds to show what he can do, picking the ball up and powering towards goal, but his shot from outside the box was comfortable for Irish keeper David Forde.
With their next attack, on three minutes, Portugal took the lead, as Silvestre Varela crossed from the right and striker Hugo Almeida rose unmarked to crash home a header.
Ronaldo's next contribution, on 10 minutes, was to slip awkwardly as he tried to turn, drawing gasps from the 46,000 crowd at the MetLife Stadium in New Jersey.
But the 29-year-old, cheered every time he touched the ball, picked himself up off the turf - no doubt to the relief of Bento and 10.5 million Portuguese.
Ronaldo was inches away from grabbing a second on 19 minutes, but his direct free kick from 20 yards pinged off the inside of Forde's post and away to safety.
A minute later it was 2-0, as a Fabio Coentrao cross was deflected off the Irish boot of Richard Keough, the ball looping over Forde and beyond his outstretched glove.
The Real Madrid striker, who missed his country's previous two warm-up games because of thigh and knee injuries, was not at his brilliant best for long periods of a one-sided friendly in the United States yesterday.