Anachronisms: One of the bounty hunters sleeps with a teddy bear ("Don't tell no one about this!") The movie is set in 1876 but teddy bears weren't invented until 1902.
Continuity: The straps on Thel's dress while she's talking to Charlie.
Crew or equipment visible: As Blake follows Nobody through a canyon, both on horseback, a crewmember is briefly but clearly seen crouched and walking between the two horses.
Factual errors: In the opening titles, after the train ride, Billy Bob Thornton's last name is incorrectly spelled "Thorton".
Continuity: When Thel is shot, her head changes position in William Blake's arms between shots.
Continuity: When William and Nobody are riding horses, William's jacket is hanging off his shoulders, in the next shot, his arms are in the sleeves, and a few shots later, his jacket is once again on his shoulders.
Continuity: Blake has a white shirt in his hand while climbing out the window, but when we see him from the outside when he falls, he no longer has it; when he lands, the shirt is seen hanging over a nearby railing.
Continuity: William Blake fires seven times from a six-shooter.
Continuity: Blake buys a half-empty bottle in the bar. Minutes later, when he offers Thel a drink outside, the bottle is filled almost to the neck.