The 'Before He Cheats' hitmaker was performing at the American Bank Center in Corpus Christi when she tripped and fell over, twisting her left foot, reported Contactmusic.
Underwood, 30, got back up again and continued the show, but later told fans she had suffered a nasty injury and feared she had broken a bone.
She also posted a picture on her Twitter page showing her foot encased in a protective cast and blamed the fall on the high-heeled boots she was wearing on stage.
"Hey, remember that time in Corpus Christi when that girl busted her butt on stage?! Hilarious! Oh wait, that was me! 5 inch heels... I can't move my toes. Is that bad?... Good news, it's not broken... And I got some new footwear!," she tweeted.