The 22-year-old pop star was performing in Saskatchewan, Canada as part of his Purpose Tour.
As Bieber walks across the stage, he steps into the gap of the open door and disappears.
After climbing out, he regains his balance. "Good thing I'm like a cat and landed on my feet," he says. "That scared the f--- outta me."
He continues through the concert, appearing to be unharmed.
Bieber said it was still a “great show” in a tweet, despite the incident.