2.3 million viewers tuned in to watch Cristiano Ronaldo's first 'Bianconeri' appearance as his side defeated Chievo Verona 3-2.
According to 'Gazzetta dello Sport', the exact figure was 2,330,234 unique viewers.
This amount is only beaten by clashes between Juventus and Inter Milan in 2013 and 2016, as well as Juventus at Roma in 2015.
The Portuguese forward failed to score in the fixture, though Allegri's side still managed to come away with a victory thanks to goals from Khedira and Bernardeschi sandwiched either side of an own goal from Chievo's Mattia Bani.
In contrast, Real Madrid saw their lowest crowd since before Ronaldo joined in 2009 for their opening 2-0 win against Getafe.
Incredibly, only 48,466 fans turned up to the Bernabeu for the game, which is just over half of the ground's attendance.
However, one reason for the abysmal attendance could be that the match kicked off at 10:15pm in Spain - an inconvenience for some fans.