School-based physical activity can promote health and improve learning outcomes, but efforts to increase school physical activity have had limited success. This study evaluates the sustainability of a multicomponent school-based physical activity intervention and identifies important factors for implementation and sustainability. Results are based on focus group interviews with 18 teachers at five implementing schools 10 months after the termination of the intervention period. The intervention comprised components related to physical education, recess, and the classroom, and focuses on inclusion for all students. The descriptive analysis of the interviews shows that the intervention is sustained with variation, and activities are adapted differently at the five schools. The deductive content analysis, based on the "Framework for Effective Implementation," reveals several important factors for sustainable implementation: School management plays an important role in setting a long-term perspective and giving the intervention priority by securing the necessary organizational infrastructure for implementation and sustainability. The teachers must find the intervention advantageous and to have clear requirements, which entail convincing communication and education by both external and internal intervention advocates. A collective start-up with training and easy-to-use materials should gradually be altered toward individual feedback and development of teachers' personal curriculum.