The current study examined relations between temperamental reactivity at 6 months and social competence in first grade, including if emotion regulation at 54 months played a role as mediator and/or moderator between temperamental reactivity and social competence in first grade. Previous studies have shown that children who are high on temperamental reactivity early on will have poorer social competence in the future (Houck, 1999). This study explored how emotion regulation might mediate this relationship as well as how emotion regulation may serve as a protective factor (e.g., moderator) for those with higher temperamental reactivity. Important background characteristics of child gender and ethnicity, mother's education, and income-to-needs ratio were controlled for. Results indicated that temperamental reactivity at 6 months did not play a significant role in social competence in first grade, nor on emotion regulation at 54 months. Emotion regulation at 54 months was also found to be neither a mediator nor a moderator between this relationship between temperamental reactivity and social competence. The only significant relationship that was found was that between emotion regulation at 54 months and social competence in first grade, which aligns with previous research. / Graduation date: 2013