Butch convinces Sundance and Etta that the three should escape to Bolivia, which Butch envisions as a robber's paradise. On their arrival there, Sundance is dismayed by the living conditions and regards the country with contempt, but Butch remains optimistic. They discover that they know too little Spanish to pull off a bank robbery, so Etta attempts to teach them the language. With her as an accomplice, they become successful bank robbers known as Los Bandidos Yanquis. However, their confidence drops when they see a man wearing a white hat (the signature of determined lawman Lefors) and fear that Harriman's posse is still after them.

Butch suggests "going straight", and he and Sundance land their first honest job as payroll guards for a mining company. However, they are ambushed by local bandits on their first run and their boss, Percy Garris, is killed. Butch and Sundance ambush and kill the bandits, the first time Butch has ever shot someone. Etta recommends farming or ranching as other lines of work, but they conclude the straight life isn't for them. Sensing they will be killed if they return to robbery, Etta decides to go back to the United States.

Butch and Sundance steal a payroll and the mules carrying it, and arrive in a small town. A boy recognizes the mules' brand and alerts the local police, leading to a gunfight with the outlaws. They take cover in a building but are both seriously wounded, after Butch makes a futile attempt to run to the mules in order to bring more ammunition, while Sundance provides cover fire. As dozens of Bolivian soldiers surround the area, Butch suggests the duo's next destination should be Australia. The film ends with a freeze frame shot on the pair charging out of the building, guns blazing, before the Bolivian forces open fire.