Match ends, Juventus 2, Sassuolo 1.
Cristiano Ronaldo scored his first two goals for Juventus as the Italian champions maintained their perfect start to the season.
Ronaldo, goalless in his first three games since his move from Real Madrid, tapped in shortly after half-time.
The 33-year-old then finished off a rapid counter-attack by shooting into the bottom corner after 65 minutes.
Sassuolo pulled one back in added time via Khouma Babacar and Douglas Costa was sent off but the hosts held on.
Juve's Brazilian winger was dismissed after a video assistant referee intervention for spitting at Federico di Francesco, having aimed a headbutt at the same player and appeared to try to elbow him.
Ronaldo could have completed a hat-trick late on but missed two easy chances from inside the penalty area.
The win is Juventus' fourth from four games this season.
The wait ends for Ronaldo
Ronaldo had been on the pitch for 320 minutes in Serie A this season before scoring his first goal since his remarkable summer move.
The wait ended with his 28th attempt of the league season but he had looked increasingly frustrated in the first half at his failure to find the net.
Ronaldo's first effort of the match in the sixth minute was blocked. He then failed to direct a header on goal and in the 27th minute struck an ambitious free-kick wide from 35 yards.
But his first goal in Juve colours could hardly have been simpler after Sassuolo failed to deal with a corner. Gianmarco Ferrari headed the ball on to his own post and it rebounded to Ronaldo unmarked inside the six-yard box for the forward to tap home.
His second was more typical as he showed excellent pace to keep up his side's counter-attack and coolly finished low past the goalkeeper.
The crowd celebrated Ronaldo's first goals for the club wildly, while the forward's girlfriend and son were also in the stands to witness the moment.
"I was a little bit anxious as expectations were high," said Ronaldo. "I really wanted to score, so I'm happy.
"Of course, there was attention after my arrival in Turin, but life is like that.
"I'm happy. I'm working well and my team-mates help me to adapt to this championship."
Costa loses his head
The game ended remarkably with substitute Costa twice to the fore, before and after Sassuolo's goal.
First the Brazilian made a dangerous lunging tackle on Di Francesco in the build-up to the goal.
As Di Francesco got to his feet Costa appeared to throw an elbow into the face of the Italian and then aimed a headbutt at the player in front of the referee.
Costa was initially shown a yellow card but, when moments later replays showed him spitting into the face of Di Francesco, he was dismissed via VAR.
Afterwards, Costa described his reaction as "ugly" and apologised to his team-mates and the club's fans on Instagram.
"I make it clear that this isolated attitude does not correspond to what I have always shown in my career," he wrote.
Juve manager Massimiliano Allegri said Costa would be fined for the incident.
"Even if he was fouled, these episodes must not happen," Allegri said.
"It's only right that he is fined, and he certainly will be. I was surprised by his reaction. We have suffered a goal, a red card and a suspension which will be long."
- 20CanceloBooked at 32mins
- 12Lobo SilvaBooked at 60minsSubstituted forJu Cuadradoat 80'minutes
- 23CanSubstituted forBentancurat 71'minutes
- 17MandzukicSubstituted forDouglas Costaat 61'minutesBooked at 90mins
- 7Cristiano Ronaldo
- 2De Sciglio
- 11Douglas Costa
- 16Ju Cuadrado
- 2Santos da Silva Barbosa
- 6Oliveira da SilvaSubstituted forDell'Orcoat 72'minutes
- 68BourabiaBooked at 40mins
- 73LocatelliSubstituted forBabacarat 83'minutes
- 25BerardiBooked at 26mins
- 9DjuricicBooked at 23minsSubstituted forDi Francescoat 61'minutes
- 34Di Francesco
- Daniele Chiffi
- Shots on Target
Second Half ends, Juventus 2, Sassuolo 1.
Douglas Costa (Juventus) is shown the red card.
Attempt saved. Domenico Berardi (Sassuolo) left footed shot from outside the box is saved in the bottom left corner. Assisted by Khouma Babacar.
Douglas Costa (Juventus) is shown the yellow card.
Goal! Juventus 2, Sassuolo 1. Khouma Babacar (Sassuolo) header from the centre of the box to the bottom right corner. Assisted by Cristian Dell'Orco with a cross.
Offside, Juventus. Wojciech Szczesny tries a through ball, but Cristiano Ronaldo is caught offside.
Attempt saved. Khouma Babacar (Sassuolo) right footed shot from outside the box is saved in the bottom left corner. Assisted by Mehdi Bourabia.
Corner, Juventus. Conceded by Cristian Dell'Orco.
Kevin-Prince Boateng (Sassuolo) wins a free kick on the right wing.
Foul by Blaise Matuidi (Juventus).
Attempt missed. Douglas Costa (Juventus) left footed shot from outside the box is close, but misses to the right.
Foul by Pol Lirola (Sassuolo).
João Cancelo (Juventus) wins a free kick in the defensive half.
Attempt missed. Domenico Berardi (Sassuolo) left footed shot from outside the box misses to the left. Assisted by Mehdi Bourabia.
Substitution, Sassuolo. Khouma Babacar replaces Manuel Locatelli.
Attempt missed. Cristiano Ronaldo (Juventus) left footed shot from the left side of the box is close, but misses to the left.
Attempt saved. João Cancelo (Juventus) right footed shot from outside the box is saved in the centre of the goal. Assisted by Blaise Matuidi.
Domenico Berardi (Sassuolo) wins a free kick in the attacking half.
Foul by João Cancelo (Juventus).