The 64-year-old recalled the excitement of Beatlemania as tribute band The Mersey Beatles performed in a replica of the Cavern Club, where the Fab Four first performed.
"Yes, I remember all the screaming fans. I remember it well," said the British royal, who was at the attraction to mark the 50th anniversary of the creation of the band.
Prince Charles' wife was greeted by well-wishers waving Union Flags and a member of staff wearing a Sgt Pepper costume.
Managing Director Jerry Goldman said: “We’re very proud that she came to visit. It was her choice to come here. She told me she saw The Beatles live many times.
“It reminded her of her youth and her teenage years . She admired the band in The Cavern.
“I think she would have stayed there for ever if she could.”