Teacher professional development (TPD) plays a vital role in enhancing student achievement and the education quality improvement at general education schools. Vietnam is carrying out the general education reforms including the curriculum, teaching methodology and textbook replacement. In order to make those reforms succeed, a lot of things have been done so far in which TPD is considered a key measure. This qualitative case-study research aimed to find out the perceptions of principals and the teachers in three selected K12 schools on TPD in response to the education reforms implementation in Vietnam using the data from the open-ended interviews with the principals, the questionnaires from teachers, and the school policy-related documents. The importance of TPD related closely to the general education reforms implementation at three schools was highly perceived and highly appreciated by the principals and teachers in similar vein. These made a strong link between their beliefs and TPD practices at their schools for promoting the education reforms.