The Take That star made the comments after meeting the third-in-line to the throne in Jamaica, where the prince was on tour as part of the Queen's Diamond Jubilee celebrations.
Upon seeing the royal being mobbed by fans upon his arrival, Barlow commented to Magic 105.4: "It was like the first incarnation of Take That.
"They were running down the streets after his car - they weren't interested in me, not a soul was interested in me. Harry is the star of the royal family, he is the Robbie of the royal family."
The X Factor judge explained how Prince Harry agreed to perform for the official Diamond Jubilee single, saying: "I said, 'So you know I'm going to see you tonight? I'm going to bring a tambourine with me. I hope you're up for it?' And he said, 'It's going to cost you!'
"So I turned up with this little tambourine in my pocket, got him to play it and spun him into the track. I think it's wonderful."
The Jubilee track, a collaboration between Barlow and Sir Andrew Lloyd Webber entitled 'Sing', was unveiled yesterday (May 18).
Prince Harry was recently rumoured to be dating The Saturdays star Mollie King, although King later denied the reports, saying that he was "out of [her] league".
Watch the video to the official Diamond Jubilee track 'Sing' below: