Early individual differences in prosocial behaviors are pivotal for children's peer relationships. To investigate the interplay among verbal ability, emotion understanding, and mother–child mutuality as predictors of prosocial behaviors, we observed 102 children at the ages of two, three, and four. All time points included verbal ability and emotion understanding tests and both video-based and maternal ratings of prosocial behavior. The first two time points also included video-based ratings of mother–child mutuality. The third time point included teacher ratings of prosocial behavior and an experimental task. Regression analysis demonstrated robust associations between emotion understanding at the age of three and prosocial behavior at the age of four. Path analysis showed that emotion understanding at the age of three mediated associations between verbal ability/mother–child mutuality at the age of two and prosocial behavior at the age of four.