Supervision of schools is concerned with the direct improvement of the work process which is viewed as a collaborative professional one among colleagues. Improving supervision of instruction in school is of great concern to educational authorities worldwide in general and particularly in Vietnam. This study investigates the understanding of supervision of instruction in twenty four primary schools in Phu Ly city, Ha Nam province from the perspectives of headteachers and teachers. Using mixed methods, data were collected by means of a questionnaire, semi-structured interview. The research revealed that the majority of headteachers and teachers shared similar concepts about instructional supervision. Evidence from the study showed that the majority of headteachers spent too much time performing their administrative and managerial duties to have enough time to effectively supervise instruction. The study also showed that teachers wanted to experience a more trusting relationship with headteachers, based on mutual respect, than they currently experienced in their schools. Recommendations about possible changes in supervisory practices will be positioned, which might in time contribute to the improvement of policy, planning and implementation of school supervision.