But the 22-year-old showed poise beyond her years, immediately brushing off the fall with a joke to the audience.
"Thank you so much," Lawrence said. "This is nuts. You guys are only standing up because I fell and you feel bad. That was embarrassing."
"What went through my mind when I fell down? A bad word that I can't say that starts with 'F,'" Lawrence told reporters after the show.
"'What do you mean, 'What happened?'" Lawrence told a reporter who asked why she fell. "Look at my dress! I tried to walk up stairs in this dress. That's what happened. I don't actually . . . I think I just stepped on the fabric and they waxed the stairs."