The teenager was performing Seven Nation Army by The White Stripes, but messed up at the opening of the song, even swearing.
"There was a lot of things that went wrong, I don't know what's going on," Becky told host Holly. "I screwed up so bad."
Becky's coach Jessie said: "You need to realise how amazing your voice is. What I'm excited about with Becky is that she hasn't even shown everything she's got."
Will.i.am commented: "It was fantastic, lots of energy, lots of energy, every note was on point. I don't know what you're worried about."
Danny said: "I'd love to duet with you, I think you're a fantastic performer, you had the crowd in your hand. I think you're pretty much there."
Sir Tom added: "She always does enough for me! This girl, Becky, is on fire as far as I'm concerned. She takes it to the extreme, so much so that I sometimes I get a little concerned with the way she sings that she may hurt her voice.
"Remember you only have one voice and you've got to hold on to it."
Watch [tag]Becky Hill[/tag] on The Voice UK below...