[SUMMARY] Purpose: To identify the problems that nursing faculty in Japan encounter while supervising master’s theses. Methods: A questionnaire was developed for this study, which included an open-ended question about the problems that nursing faculty encounter in their supervision of master’s theses. Six hundred and ninety questionnaires were distributed to faculty working at graduate schools of nursing in Japan by mail and a researchers’ network. Responses were analyzed qualitatively. Results: The number of questionnaires returned was 219, of which 210 answers to open-ended questions, in addition to 19 pilot study answers, were analyzed qualitatively. As a result, 32 categories, representing the problems that nursing faculty in Japan encounter while supervising master’s theses, were formed. The agreement rates calculated using Scott's formula, were 81.8% and 72.7%. Conclusion: As a result of considering each problem encountered by nursing faculty supervisors, 32 problems were categorized into seven major types according to the causes of the problems. Nursing faculty can use the results of this study to objectively understand these problems in the supervising process and their causes, which may lead to overcoming problems in their own situations and improving their research supervision abilities.