Drawing on Sutton and Levinson's Socio-cultural Approach to policy, this study explores the experiences and collective language beliefs of 25 teachers implementing the Mother Tongue-Based Multilingual Education (MTBMLE) policy in two urban Philippine school districts. Mixed methods were used to understand policy enactment and teacher perspectives. Findings reveal that teacher beliefs about language significantly influence their appropriation of the MTBMLE policy. While some teachers accommodated the policy, others demonstrated negotiation and some showed nuanced resistance due to perceived pedagogical challenges hindering implementation. This research highlights the role of teachers as active agents in shaping policy, not simply passive recipients. By uncovering teachers' deeply held language ideologies, the study offers valuable insights for MTBMLE policy reformulation.