Situated in the education reform launched by the Egyptian Ministry of Education (MOE), which called for a socially-foreign shift away from memorization-based mathematics instruction, this paper explores the role of school-based teacher professional networks in implementing reform. Adopting the Goodson Change Model as a theoretical framework, we map out the power play between external agency (national society), internal agency (teacher professional networks) and the personal agency of individual teachers. Using an embedded case study model and a dataset consisting of the recordings of two full-day focus group discussions with teacher professional networks at two national schools, we contrast the two cases from the perspective of teacher group tensions and power dynamics in relation to the reform implementation. In one case, the teacher professional network (internal agency) was dominantly embracing the change, thus empowering the local teacher (personal agency) and enforcing its dogma on its stationed national society (external agency). In the other case, the teacher as a personal agent was solely attempting to break through both layers of internal and external agency. Our findings cast light on the role of teacher professional networks in curricular reform contexts, particularly within a collective cultural setup such as Egypt. Implications for the role of teacher professional networks in the diffusion of reform initiatives are discussed in light of the findings.