The study of prosocial behavior, from the cognitive-evolutive approach, has indicated that moral reasoning is the basis of prosocial decisions. Advances in the study of decision-making have shown that there are other factors associated with rational capacity that affect prosocial decision-making. The role of rational decision-making is an aspect that has received little attention from this perspective and could be relevant to explaining prosocial behaviors. This study examines whether rational decision-making is a potential mediator between empathy and prosocial behavior in offenders adolescents. A total of 413 Colombian adolescent offenders aged 14 to 18 years ( M age = 16.67, SD = 1.05, 17.4% were girls) participated in the study. They belonged to Colombia’s four regions (Antioquia, Caldas, Cundinamarca, and Bogotá, the Capital District). Empathy, decision-making, and prosocial behavior were assessed with self-reports. Confirmatory factor analysis of the scales used, descriptive, correlational, predictive, and mediation analyses were performed. The results indicated positive relationships between the variables empathy, rational decision-making, and prosocial behavior. In the mediation analyses, empathic concern and personal distress were the background variables with the greatest effect on prosocial behavior when mediated by rational decision-making. The results indicate that having greater rational decision-making ability may help adolescent offenders display prosocial behaviors. Results, limitations, and practical implications for adolescent counseling are discussed, and future research suggestions are made.