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.