The former United star helped to set up Juve's winner in the 17th minute, with his cross reaching the Argentine striker who swept home a clinical finish from close range.
The seven time defending Italian champions - who dropped their first points of the season in the league on Saturday - maintained their 100% record and showed why they are considered as strong favourites to go all the way in this season's Champions League. The two sides meet agai at the Allianz Stadium on 7 November, when a win will send Juve into the last 16.
United remain in second place, with their hopes of making the knockout stages boosted by Valencia's draw with Young Boys earlier on Tuesday.
Max Allegri's men took the lead with the first attack of the game with Ronaldo - almost inevitably -involved.
His cross from the right saw a coming together between Juan Cuadrado and the stretching Smalling, but the loose ball broke for Dybala to snaffle up the gift of a simple finish from eight yards.
Paul Pogba - also against his former employers - headed wide from an Ashley Young free-kick, but the continuous flow of black-and-white clad traffic continued to pour towards the Stratford End.
David de Gea came to United's rescue seven minutes before the break when he beat away a trademark gunslinger Ronaldo set-piece, before the stopper also reacted strongly to thwart Blaise Matuidi on the rebound.
United had become a second-half team in the last two matches and the stadium was hoping the Reds might be able to respond after the interval. Juventus had other ideas, though, and the break did nothing to quell their superiority.
Once again it was thanks to De Gea that the Italians were still within reach. The ‘keeper got a touch on a typical Ronaldo thunderbolt after 52 minutes to stop the no.7 celebrating a goal at Old Trafford again. Dybala went close with a header and his replacement, Federico Bernardeschi, fired wide shortly after he had come on.
Despite a brief flurry of United pressure, Juventus and their keeper - former Arsenal man Wojciech Szczensy - were never seriously tested. Pogba, one of only three United players to perform well on the night, came closest when his drive from distance struck a post, bounced off Szczesny and went for a corner. A weak Anthony Martial effort offered up the Reds only response from then on, as the Italians did what they do best and managed the tie to perfection.
Overall team performance: 6/10
United Faithful Man of the Match: Victor Lindelof