Universally, social norms prescribe behavior and attitudes, but societies differ widely in how strictly individuals adhere to the norms and punish those who do not. This paper shows that collective traumatic experiences, henceforth ``disasters”, lead to stricter adherence to social norms. To establish this result, I combine data on the occurrences of conflicts, epidemics, and natural and economic disasters with the World Value Surveys and European Social Surveys. I use this data set to estimate the effect of disasters on norm adherence in two ways: $(i)$ investigating event-studies that compare individuals interviewed in the days before and after the same disaster; and $(ii)$ examining variation in individuals’ past exposure to disasters across countries and cohorts while controlling for country-, cohort-, and life-cycle-specific factors. The event-studies demonstrate that disasters strengthen adherence to social norms by 11 percent. The analysis of cross-country variation shows that the effect is long-lasting, often for several decades. Consistent with a model in which social coordination is beneficial when disasters threaten the success of entire groups, the effect of disasters on norm adherence is more pronounced in low-income countries, where survival is less secure. The results suggest that past exposure to disasters partially explains within-group cohesion and, if groups have different norms, between-group divides.