Punishment can reform uncooperative behavior and hence could have contributed to humans’ ability to live in large-scale societies. Punishment by unaffected third parties has received extensive scientific scrutiny because third parties punish transgressors in laboratory experiments on behalf of strangers that they will never interact with again. Often overlooked in this research are interactions involving people who are not strangers, which constitute many interactions beyond the laboratory. Across three samples in two countries (United States and Japan; N = 1,294), we found that third parties’ anger at transgressors, and their intervention and punishment on behalf of victims, varied in real-life conflicts as a function of how much third parties valued the welfare of the disputants. Punishment was rare (1–2%) when third parties did not value the welfare of the victim, suggesting that previous economic game results have overestimated third parties’ willingness to punish transgressors on behalf of strangers.