Abstract: See injustice and draw your sword against it. Since its proposal, the belief in a just world theory has focused on the phenomenon, yet its theoretical hypotheses and empirical findings remain inconsistent. To resolve this controversy and uncover the reasons for the divergent results, we conducted a three-level meta-analysis to systematically examine the effects between belief in a just world and third-party punishment and the moderating variables in the relationship. Through literature search and screening, a total of 46 research papers with 93 effect sizes were included, and the total sample size was 15,772 participants. Main effect analyses revealed that belief in a just world positively predicts third-party punishment. Moderator analyses indicated that the effect was moderated by the self–other dimension of BJW, cultural background, the violation scenarios and sample types but was not by observers' gender, observers' age, and the explicit–implicit dimension of BJW. These findings contribute to addressing the competing hypotheses of the belief in a just world theory and specifying its boundary conditions, offering valuable insights for future theoretical development and empirical research.

Key words: belief in a just world, third-party punishment, three-level meta-analysis, moderating effect.