The purpose of this study was to determine the association between the occurrence of stressful life events and internalizing and externalizing problems, and to analyze longitudinally buffering effects of supportive family relationships. To this end, 100 Spanish adolescents were studied twice, when they were in mid-adolescence (15-16 years) and two years later. They completed questionnaires regarding stressful life events, family relationships, and adolescent adjustment. Results showed that high quality parent-adolescent relationships protected boys and girls against the negative consequences of stressful life events on externalizing, but not internalizing, symptoms. The adolescents who enjoyed good relationships with their parents in mid-adolescence did not increase their externalizing problems in late adolescence as consequence of the occurrence of stressful events. However, these stressors did lead to an increase in the number of externalizing problems when the family relationships were of a middle or low quality. These results highlight the important role that supportive family relationships play in the behavioral adjustment of adolescents, protecting them against some negative consequences of stressful life events, and suggest the relevance of supporting parents through resources such as parent education in order to help them to improve their relationships with their adolescents.