"Ed is a quick study...turned out great".
The ‘American Pie’ icon, 72, joined forces with Sheeran as they relaxed backstage at a UCLA Health and Teen Cancer America benefit concert on Saturday.
In the footage, Sheeran is seen strumming his guitar to the iconic hit, while he and McLean take it in turns to sing the verses before finally duetting on the chorus.
“Ed & I rehearsing Vincent for the big show!”, McLean captioned the video.
“Ed is a quick study…turned out great”.
Responding to the video, one fan wrote: “This is sublime. Thank you for posting it.”
Meanwhile, it was reported last month that Sheeran is the world’s highest earning solo musician.
The 27-year-old pop star is worth $110 million (£83 million) and has been ranked ninth on Forbes’ annual list of the world’s best paid celebrities.
In 2017, ‘Shape of You’ became Spotify’s most streamed track of all time.
As for McLean, he proved to be an outspoken critic of the Me Too movement earlier this year, describing it as “disingenuous”.