The Seleccao captain was missed by his team in their last warm-up match, a 0-0 draw against Greece at the Estadio Nacional.
The Real Madrid star had to watch from the stands due to a minor thigh problem, which has been troubling him since the closing stages of last season.
But the result doesn't seem to have affected squad spirit - Ronaldo posting the photo with the caption "a team representing a country!"
Paulo Bento's men will take on Mexico and the Republic of Ireland next, before their World Cup opener against heavily-fancied Germany.
The United States and Ghana are their other opponents in a tough-looking Group G.