Purpose <p>Domestic and intimate partner violence (DIPV) is a global health crisis that remains vastly underreported, making community bystanders a critical avenue for prevention. Understanding what shapes individuals’ sense of responsibility to intervene is essential, yet bystander research has been dominated by Western theory. This study examines how culture moderates the bystander effect on perceived responsibility in DIPV situations and explores psychosocial barriers informing this judgment.</p> Methods <p>A vignette-based experiment was conducted with participants from the United Kingdom (<i>N</i> = 242) and China (<i>N</i> = 221). Participants were randomly assigned to one of three third-person vignettes depicting a bystander witnessing DIPV: alone, with multiple passive bystanders, or in a control condition. The primary outcome was perceived responsibility, with predictors including demographic variables and four barrier subscales (normative, reputational, relational, safety).</p> Results <p>A two-way ANOVA revealed a significant culture × condition interaction. UK participants displayed a classic bystander effect, reporting lower responsibility when others were present, whereas Chinese participants reported higher responsibility in the multiple-bystander condition, indicating a reversed bystander effect. Regression analyses showed that normative concerns were the only consistent barrier predicting lower responsibility, with this effect stable across cultures. Culture itself remained an independent predictor, with Chinese participants reporting lower baseline responsibility than UK participants.</p> Conclusions <p>The bystander effect is not universal but fundamentally shaped by culture. These findings challenge classic bystander theory and caution against directly exporting Western-developed intervention programs. Effective prevention demands cultural specificity, recognizing the diverse ways responsibility is constructed across communities.</p>