The 43-year-old Britain's Got Talent judge was researching for This Morning, where she is covering Holly Willoughby's maternity leave.
Just before going off to interview Lady Gaga and Tony Bennett, Amanda shared a snap of her from behind, showing her purple dress unzipped up to her lower back and showing off her bum.
She wrote: "Guess who I interviewed today? #cheeky"
Meanwhile the presenter recently spoke about filling in for Holly, who recently welcomed her baby boy Chester, and having to be professional on live telly.
She told the Mirror: "You have to be really careful with live television.
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"I've got these lovely girls and boys on Twitter, they're called the Holdenites, and as a present they gave me a swear jar.
"There's no money in it at the moment 'cos I'm doing really well. I seem to have found a filter – which is a first for Mandy!"
Speaking previously about covering Holly, Amanda said: "I am over the moon to get a chance to present on of my favourite shows on TV and I'm thrilled to be keeping Holly's seat on the sofa warm while she goes off on maternity leave.
"I've always been a huge fan of This Morning and love presenting with Phillip so I really can't wait to get started."