Our goal was to conduct international comparisons of emotion regulation using the 9-item Emotionally Reactive (ER) syndrome of the Child Behavior Checklist for Ages 11/2-5. We analyzed parent ratings for 17,964 preschoolers from 21 societies, which were grouped into 8 GLOBE study culture clusters (e.g., Nordic, Confucian Asian). Omnicultural broad base rates for ER items ranged from 8.0% to 38.8%. Rank ordering for mean item ratings varied widely across societies (omnicultural Q = .50) but less so across culture clusters (M Q = .66). Societal similarity in mean item rank ordering varied by culture cluster, with large within-cluster similarity for Anglo (Q = .96), Latin Europe (Q = .74), Germanic (Q = .77), and Latin American (Q = .76) clusters, but smaller within-cluster similarity for Nordic, Eastern Europe, and Confucian Asian clusters (Qs = .52, .23, and .44, respectively). Confirmatory factor analyses of the ER syndrome supported configural invariance for all 21 societies. All 9 items showed full to approximate metric invariance, but only 3 items showed approximate scalar invariance. The ER syndrome correlated . 65 with the Anxious/Depressed (A/D) syndrome and .63 with the Aggressive Behavior syndrome. ER items varied in base rates and factor loadings, and societies varied in rank ordering of items as low, medium, or high in mean ratings. Item rank order similarity among societies in the same culture cluster varied widely across culture clusters, suggesting the importance of cultural factors in the assessment of emotion regulation in preschoolers.