The present study investigated how school support was related to teachers' motivation and willingness to persist in project-based learning. The participants were 182 Hong Kong teachers who completed a questionnaire about their school's support and their motivation to implement project-based learning. The results of structural equation modeling indicated that when teachers perceived their schools as being stronger in collegiality and more supportive of teacher competence and autonomy, they had higher motivation in project-based learning and stronger willingness to persist in this educational innovation. Perceived school support predicted teachers' attitude for future persistence both directly and indirectly through its influence on teacher motivation. The results suggest that social-contextual factors are important for teacher motivation in the implementation of educational innovations.