There were concerns that the Portugal international would not be able to shake off a thigh injury in time to feature in Wednesday's showdown with the Dutch side.
He did, however, take part in training with the rest of the squad on Tuesday and was subsequently part of the travelling party heading to Amsterdam.
There is less positive news over the fitness of captain Chiellini, however.
And he has since been ruled out of the first leg, with Chiellini's name not part of the 21-man squad named to face the Eredivisie side.
Former Liverpool midfielder Emre Can is also missing after he had to train separately from the rest of the squad on Tuesday as he continues to struggle with an ankle problem.
That could see Sami Khedira, who only recently returned to action following a heart problem, take his place in the starting XI in what would be his first start since February 15.
Should, as now expected, Ronaldo feature from the start against Ajax, it will be his first appearance for Juve in four matches.
Having been rested for the 2-0 defeat to Genoa, Ronaldo subsequently injured his hamstring on international duty with Portugal where he had to be withdrawn after 30 minutes of the 1-1 Euro 2020 qualifying draw with Serbia.
With the Serie A title all but clinched, Massimiliano Allegri's side will be hoping they can make significant progress in Europe and, should they manage to advance past Ajax, they will then face either Manchester City or Tottenham in the semi-finals.
And they will likely be looking to Ronaldo for inspiration, with the 34-year-old scoring an incredible hat-trick to ensure Juve recovered from a 2-0 first-leg deficit to beat Atletico Madrid and advance through to the quarters.