Background and aim <p>Violence in hospital emergency rooms (ERs) presents serious risks to patient safety and healthcare workers. While prior research has focused on organizational risk factors, limited attention has been given to how the public interprets and accepts violent behavior, particularly across different generations. This study examined generational differences in perceptions and acceptance of violent behavior in hospital ERs in Thailand.</p> Methods <p>A cross-sectional survey was conducted among 615 residents living in communities surrounding seven hospitals. Respondents were classified into four generational cohorts: Generation Z, Millennials, Generation X, and Baby Boomers. Data were collected using a structured questionnaire based on the Theory of Planned Behavior. Data analysis included descriptive statistics, Chi-square tests to examine severity classifications, and multiple regression analysis with dummy-coded generational variables (Baby Boomers as reference group) to examine the association between each generational cohort and acceptance of violence. Bias-corrected bootstrapping was employed to validate confidence intervals for all estimates.</p> Results <p>Chi-square results indicated significant generational differences in how violence is defined; younger cohorts were more likely to label only physical assault as violence, while overlooking verbal aggression. Multiple regression analysis indicated that, relative to Baby Boomers (reference group), Generation Z (B = 0.263, β = 0.187, <i>p</i> = .019) and Millennials (B = 0.230, β = 0.155, <i>p</i> = .045) were significantly associated with higher acceptance of violent behavior in ERs, while Generation X did not differ significantly (B = 0.100, β = 0.062, <i>p</i> = .393). Overall model: F(3, 611) = 3.075, <i>p</i> = .027, R² = 0.015.</p> Conclusions <p>Generational background is significantly associated with differences in how individuals interpret and accept aggression in hospitals. Current Zero Tolerance policies may have limited effectiveness because younger demographics do not perceive verbal aggression as a violation. Prevention strategies may benefit from explicitly defining and prohibiting non-physical violence to align with the interpretive frameworks of younger generations.</p> Clinical trial registration <p>Not applicable.</p>