Higuain endured a personal nightmare against his parent club, seeing a penalty saved and being dismissed late on at San Siro on Sunday.
The Argentina attacker had to be led off the field after a meltdown following referee Paolo Mazzoleni's decision to send him off.
But Ronaldo, who scored the second goal in Juve's victory over the Rossoneri, said Higuain should not be punished too heavily.
"I told him to calm down, as he risked an even worse ban," Ronaldo said to Sky Sport Italia.
"He didn't do much, he was annoyed at losing the game. That's understandable. I hope he is not punished too severely."
Champions League (@ChampionsLeague) November 11, 2018
Juventus bounced back from their first loss of the season, at home to Ronaldo's old club Manchester United in the Champions League, last time out.
Mario Mandzukic opened the scoring with Ronaldo's sixth goal in seven Juve appearances clinching all three points for Juve, who have set a Serie A record with 34 points from their opening 12 games in a strong start to their title defence.
"We played well, I also scored... I'm really happy to help the Juventus family. Good team performance, against a difficult Milan."