The US singer and NFL player husband Travis Kelce, both 36, tied the knot at New York's Madison Square Garden on July 3.
More than 1000 guests attended the event including McCartney, who performed a rendition of The Beatles song I Want To Hold Your Hand.
The single, released in 1964, was the band's first number one single in the US and was credited with sparking Beatlemania there after they performed the song on The Ed Sullivan Show.
Now McCartney has revealed more about performing at Swift's wedding.
Appearing on Jimmy Kimmel Live!, he shared that the singer had requested he sing the song, but he also asked her to join him.
"She was on stage and I said, 'you should sing along, and you should sing it to your man'," he said.
Kimmel replied: "Seems like reasonable advice!"
In 2024, McCartney was seen attending one of Swift's Eras Tour shows at Wembley Stadium in London.
In March 2026, she then went to McCartney's concert at the Fonda Theatre in Los Angeles.
While appearing on BBC Radio 2's Tracks Of My Years in May 2026, McCartney also praised Swift.
"Taylor (Swift) is very good. She's very clever," he told host Vernon Kay.
Comparing her success with what The Beatles experienced, he added: "You do see the parallel, you know like, fame and the amount of fame, and the worldwide fame that Taylor Swift has and that we had.
"But, I don't think she needs any advice, to tell you the truth."
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