This qualitative study aims to uncover the characteristics of teacher professional development (TPD) among professional groups of Vietnamese primary schools in the context of educational reform in the light of a sociocultural perspective. Data were collected from 12 participants from four primary schools in Central Vietnam using in-depth interviews. The participants comprised one principal, one team leader and one teacher from each school. Qualitative analysis of the data showed that three characteristics of TPD, namely self-directedness, collegiality and situatedness, were evident in the professional activities of primary school teachers. The participants also reported that most teachers were active in professional activities. However, the participants reported several challenges hindering teachers from actively participating in professional learning communities. These challenges included inflexibility due to old age, limited access to information technology, financial difficulties, or unsupportive family conditions. The results also revealed that the professional activities of the groups were influenced by the school's leadership. The collegiality of teachers in professional activities was relatively high. Proficient teachers often played a leading role in professional activities. This study serves as an initial attempt to enhance teacher professional development programmes for primary school teachers in Vietnam, and beyond.