The 38-year-old Oscar-winning actress, who sang Forget You with Cee Lo Green at the February awards show, talks about the experience in the September issue of US Elle.
'This story always makes me cry,' says the Country Strong star, as she reveals that the R&B star was on hand while she did her pre-show sound check.
'It's 10 in the morning and Beyoncé schleps it all the way down to the Staples Centre to watch.'
The Single Ladies singer, who filmed Paltrow's performance on her iPhone, also gave her friend some helpful advice.
'Beyoncé's like, 'OK. The singing is great, but you're not having any fun'. She's like, 'Remember when we were at Jay's concert and Punjabi MC comes on and you do your crazy Indian dance? Do that. Be you!' I was like, 'I don't know how to do that'. She's like, 'Yes, you f****** do'.'
And according to the Iron Man 2 star, Beyoncé's rapper husband apparently agreed with his wife, after she emailed the video to him of Paltrow singing.
'He was like, 'Stop being so nice!'' she reveals.
The mum-of-two, who says she had a pint of Guinness with a beta-blocker for Dutch courage before taking to the stage at the awards show, also revealed that her husband, Coldplay frontman Chris Martin, acknowledged the challenge she had set herself.
She says: 'My husband told me, 'Most people start performing first at a pub and their uncle is there and their friends from the dorm'.'