This article examines the impact of implementing module-based professional development for teachers (MBPDT) in the Philippines. A mixed-method study, experimental design with empirical surveys and an open-ended questionnaire revealed that the experimental group of teachers had greater professional content knowledge compared with the control group after five weeks of implementing MBPDT. However, the experiment did not yield significant effects on the teachers' commitment levels or on their pupils' mathematics proficiency levels. Another significant finding showed that the more experienced teachers in the experimental group possessed slightly higher commitment after the intervention. Finally, results of the study suggest that a larger scale implementation of MBPDT may be undertaken as a cost-effective option for teachers' professional development.