Emotion regulation is an important aspect of children's development. Using Second Step, a curriculum aimed at assisting children's development of emotion regulation and prosocial behaviors in the classroom, this study examined individual differences in children's responsiveness to a social skills intervention. One such individual difference in personality, Agreeableness, reflects a person's motive to maintain smooth relationships with others. Significant differences in children's responsiveness to intervention were hypothesized for children low, medium, and high in Agreeableness. Responsiveness was assessed using three different measures: behavioral observations, teacher reports, and Second Step knowledge tests. Individual and situational differences are discussed in light of the results, and directions for future research are proposed.