Fabio Miretti scored the only goal in the 10th minute on Sunday (Monday AEDT), firing Filip Kostic's cross into the bottom corner. It was a first senior goal for the 20-year-old, who has been at Juventus since he was eight.
Juventus have not conceded a goal for six straight matches.
A section of hardcore Fiorentina fans boycotted the match in protest as they felt it shouldn't have gone ahead at a time when the Tuscany region is struggling after devastating floods in the wake of Storm Ciaran.
They left their seats empty at one end of the stadium and were instead working to help clear the mud and standing water from homes and businesses.
There was a minute's silence before all Serie A matches this weekend in memory of the victims. In Florence, the two teams — normally fierce rivals — mixed together during that moment to show their solidarity.
Fiorentina drop to eighth, level on points with Roma who scored two added-time goals to snatch a 2-1 win over Lecce.
Striker Romelu Lukaku lost his perfect penalty record in Italy though, but made up for it with a last-minute winner.
The Belgian should have got the hosts off to the perfect start but his spot kick was saved by Lecce goalkeeper Wladimiro Falcone inside five minutes.
It was the first penalty Lukaku had failed to convert in Serie A, having scored 14 times from the spot for Inter.
Lecce broke the deadlock in the 71st minute when Lameck Banda raced down the left and got the ball to Pontus Almqvist, who swept it into the bottom left corner.
It appeared as if the visitors were heading to their first win in seven matches, but Iranian substitute Sardar Azmoun headed in Nicola Zalewski's cross in the first minute of added time.
And the crowd at the Stadio Olimpico went from despair to delight in less than three minutes as Lukaku then curled Dybala's through ball into the top left corner.
Elsewhere, relegation battles saw Cagliari beat Genoa 2-1 and Hellas Verona lose 3-1 to Monza.
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