UK Police launched a probe after a clip was circulated online of Ronaldo appearing to knock a supporter's mobile phone on to the ground as he limped towards the tunnel following United's 1-0 loss.
Cristiano Ronaldo has been cautioned by British police after footage emerged of the Manchester United forward appearing to smash a phone out of an Everton fan's hand at a match last season.
The 37-year-old was interviewed by officers in relation to an allegation of assault and criminal damage following the incident at Goodison Park on April 9.
The Merseyside Police said in a statement on Wednesday: "We can confirm that a 37-year-old man voluntarily attended and was interviewed under caution in relation to an allegation of assault and criminal damage."
"The allegation relates to an incident following the Everton v Manchester United football match at Goodison Park on Saturday April 9.
"The matter has been dealt with by way of conditional caution. The matter has now concluded."
After the incident, Ronaldo issued a social media apology for his "outburst" and invited the supporter to watch a game at Old Trafford "as a sign of fair-play and sportsmanship".
An outburst and an apology
Taking to his Instagram account after the match, the Portuguese forward said: "It's never easy to deal with emotions in difficult moments such as the one we are facing.
"Nevertheless, we always have to be respectful, patient and set the example for all the youngsters who love the beautiful game.
"I would like to apologise for my outburst and, if possible, I would like to invite this supporter to watch a game at Old Trafford as a sign of fair-play and sportsmanship."
It comes as Ronaldo hit out at the "lies" surrounding reports about his future at struggling United.
The Portugal forward missed the club's pre-season tour to Thailand and Australia for personal reasons as speculation swirled over whether he would be leaving Old Trafford.
It has been reported Ronaldo wants to play Champions League football, but United maintain he is not for sale and remains an integral part of the plans of new boss Erik ten Hag.
The former Real Madrid star played the full 90 minutes of United's 4-0 defeat at Brentford on Saturday, which left them bottom of the Premier League.
In a reply to a fan account on Instagram that referred to a report linking the United frontman to Atletico Madrid, Ronaldo said fans would "know the truth" in a couple of weeks, adding: "The media is telling lies."