A meta-analysis of gender differences in emotion expression in children (ages 0–17) found small but significant gender differences. Girls showed more positive emotions (g = -.08) and internalizing emotions (e.g., sadness, anxiety; g = -.10) than boys, while boys showed more externalizing emotions (e.g., anger; g = .09) than girls. These differences were moderated by age, interpersonal context, and task valence. Gender differences in positive emotions increased with age, with girls showing more positive emotions than boys in middle childhood (g = -.20) and adolescence (g = -.28). Boys showed more externalizing emotions than girls in toddler/preschool age (g = .17) and middle childhood (g = .13), but fewer externalizing emotions than girls in adolescence (g = -.27). Gender differences were less pronounced with parents and more pronounced with unfamiliar adults (positive emotions) and peers/when alone (externalizing emotions). The findings highlight the importance of contextual factors in gender differences in emotion expression, with implications for understanding healthy and maladaptive development in children. Theories suggest that biological factors, socialization, and contextual influences shape gender differences in emotion expression. The study used Hedges' g as the effect size measure and conducted random effects models to account for variability among studies. The results indicate that while gender differences in emotion expression are small, they are significant and influenced by developmental stage, social context, and task characteristics.A meta-analysis of gender differences in emotion expression in children (ages 0–17) found small but significant gender differences. Girls showed more positive emotions (g = -.08) and internalizing emotions (e.g., sadness, anxiety; g = -.10) than boys, while boys showed more externalizing emotions (e.g., anger; g = .09) than girls. These differences were moderated by age, interpersonal context, and task valence. Gender differences in positive emotions increased with age, with girls showing more positive emotions than boys in middle childhood (g = -.20) and adolescence (g = -.28). Boys showed more externalizing emotions than girls in toddler/preschool age (g = .17) and middle childhood (g = .13), but fewer externalizing emotions than girls in adolescence (g = -.27). Gender differences were less pronounced with parents and more pronounced with unfamiliar adults (positive emotions) and peers/when alone (externalizing emotions). The findings highlight the importance of contextual factors in gender differences in emotion expression, with implications for understanding healthy and maladaptive development in children. Theories suggest that biological factors, socialization, and contextual influences shape gender differences in emotion expression. The study used Hedges' g as the effect size measure and conducted random effects models to account for variability among studies. The results indicate that while gender differences in emotion expression are small, they are significant and influenced by developmental stage, social context, and task characteristics.