Purpose: Adolescents' and parents' experiences within a multidimensional school-based physical activity intervention grounded on self-determination theory were explored. Method: Qualitative data from 29 adolescents (aged 15-17 years) and three parents on behalf of the total students' families were collected via participant observation (research diary), semistructured interviews, and focus groups. Results: Adolescents perceived that the application of motivational strategies, based on self-determination theory, satisfied their basic psychological needs for autonomy, competence and relatedness, favored self-determined motivation, and gave rise to adaptive consequences (improved physical activity knowledge, creation of affective bonds, and increased leisure-time physical activity). These results were supported by the information reported by the students' parents. Discussion/Conclusions: The findings support the implementation of self-determination theory-based multidimensional interventions to promote adolescents' physical activity participation. This study also presents several motivational strategies which could be useful for the design and implementation of future school-based physical activity interventions.