The incident occurred shortly after full-time of the match at BayArena, with a selfie-hunting supporter gaining access to the pitch having bypassed security officials.
As Ronaldo chatted with team-mate Miralem Pjanic, the fan came up behind the five-time Ballon d’Or winner with a mobile phone and tried to put his arm around the Portugal star’s neck.
Ronaldo managed to evade the supporter before showing his disgust, with the fan eventually being led away by security.
It was the second pitch-invader incident involving Ronaldo, with a fan having previously been apprehended trying to reach the 34-year-old earlier on in the evening.
Juventus had already qualified for the Champions League last 16 as group winners, but still got the job done with two second-half goals in Germany.
And it was Ronaldo who put his side ahead on 75 minutes with a tap-in after Paulo Dybala’s cross.
Despite Leverkusen having a golden chance to equalise through Charles Aranguiz as full-time approached, Gonzalo Higuain sealed all three points with a low drive in stoppage time.
After topping their Champions League group, Maurizio Sarri’s side could now face Real Madrid, Tottenham, Dortmund, Lyon or Chelsea in the first knockout round.
Juve may be cruising in Europe but it’s a different story in Italy as they sit second in the Serie A table, two points behind Inter, despite only losing one game so far.
They have won the last eight Italian top-flight titles but appear to be in for a battle with Antonio Conte’s side this season.
The Turin club now face league matches against Udinese and Sampdoria before travelling to Saudi Arabia for a Supercoppa Italiana clash against Lazio before the Christmas break.
Ronaldo, meanwhile, has not featured in every game for Juve this season, with Sarri opting to rest the former Real Madrid man on occasion.
The former Real Madrid forward has nine goals from his 18 matches across all competitions for the Italian giants in 2019-20, with seven of them coming in the league.