The present study aimed at investigating the role of the supervisor of Islamic Education in the professional growth of secondary school teachers of Islamic Education. A randomly. chosen sample was selected from the total population of teachers of Islamic Education in six Omani educational zones was used for the purpose of this study. This sample consisted of 120 male and female teachers. Another randomly chosen sample of supervisors of Islamic Education was selected for the purpose of this study. This sample comprised 44 male and female supervisors. Two questionnaires were developed for the purpose of this study: a questionnaire comprising 40 items under six main dimensions for teachers and another questionnaire consisting of 27 items for supervisors. The aim was to identify the difficulties that reduce the effectiveness of the supervisor's role in the professional growth of teachers of Islamic Education. The validity and reliability of these two instruments were established. Means and standard deviations were used in data analysis. The role of the supervisor was most effective in the objectives domain and in the social relationship domain. It was found to be least effective in the domain of instructional media, teaching methods and educational activities. The study revealed that the most serious difficulty that reduces the effectiveness of the supervisor's role in teachers' professional growth is that there are no special meeting rooms for supervisors. The least serious difficulty is the weakness of social relationships between teachers and supervisors. Recommendations for getting over the difficulties that reduce the effectiveness of the role of the supervisor were made. The study also provides a proposed framework for supervision in Islamic education.