Bidirectional relations among adolescents’ positivity, perceived positive school climate, and prosocial behavior were examined in Colombian youth. Also, the role of a positive school climate in mediating the relation of positivity to prosocial behaviors was tested. Adolescents (N = 151; Mage of child in Wave 1 = 12.68, SD = 1.06; 58.9% male) and their parents (N = 127) provided data in two waves (9 months apart). A model of bidirectional relations between positivity and perceived positive school climate emerged. In addition, adolescents with higher levels of perceived positive school climate at age 12 showed higher levels of prosocial behaviors in the following year. Positive school climate related positivity to adolescents’ prosocial behavior over time.