This study investigates the relationship between empathic distress and concern in toddlers and their predictive effects on physical aggression at ages 20 and 30 months, while considering sex differences. The study used a longitudinal design, observing empathic behavior during a distress simulation task at age 20 months and assessing physical aggression through maternal reports at ages 20 and 30 months. Empathic distress and concern were measured using behavioral responses to the distress simulation task, and physical aggression was assessed using the Physical Aggression Scale for Early Childhood. Linear regression analyses revealed that empathic distress and concern were associated with less physical aggression in girls but not in boys. Specifically, higher levels of empathic distress at age 20 months predicted lower levels of physical aggression in girls at ages 20 and 30 months, while controlling for physical aggression at age 20 months. Empathic concern was marginally positively associated with physical aggression in boys but negatively associated with physical aggression in girls at age 20 months. The findings suggest that the prediction of physical aggression by empathic distress is more robust over time than by empathic concern. The study highlights the importance of empathic distress in predicting aggression in toddlers and provides insights into the complex relationship between empathy, aggression, and sex from a developmental perspective.This study investigates the relationship between empathic distress and concern in toddlers and their predictive effects on physical aggression at ages 20 and 30 months, while considering sex differences. The study used a longitudinal design, observing empathic behavior during a distress simulation task at age 20 months and assessing physical aggression through maternal reports at ages 20 and 30 months. Empathic distress and concern were measured using behavioral responses to the distress simulation task, and physical aggression was assessed using the Physical Aggression Scale for Early Childhood. Linear regression analyses revealed that empathic distress and concern were associated with less physical aggression in girls but not in boys. Specifically, higher levels of empathic distress at age 20 months predicted lower levels of physical aggression in girls at ages 20 and 30 months, while controlling for physical aggression at age 20 months. Empathic concern was marginally positively associated with physical aggression in boys but negatively associated with physical aggression in girls at age 20 months. The findings suggest that the prediction of physical aggression by empathic distress is more robust over time than by empathic concern. The study highlights the importance of empathic distress in predicting aggression in toddlers and provides insights into the complex relationship between empathy, aggression, and sex from a developmental perspective.