Medical waste management (MWM) is an important public health concern worldwide. Although physicians must participate in medical waste management, their personal and organizational predictors in this process are unknown. This study aimed to the determinants of physicians' knowledge, attitudes and practices related to MWM in eight hospitals of Mazandaran province, northern Iran. A validated, reliable self-administered questionnaire was used including 30 questions about the respondents' knowledge, attitudes and practices (KAP) and personal and professional variables. Of a total of 200 physicians, 150 persons completed the questionnaire (response rate of 75%). The average score (± SD) for physicians' knowledge was 6.50 (± 1.50) out of 10, whereas those for attitudes and practices were 4.44 (± 0.88) and 4.02 (± 1.35) out of 5, respectively. Surgeons and orthopaedists had the lowest scores, whereas para-clinical specialists and internal medicine specialists had the highest scores. The score of knowledge showed significant differences among speciality groups and the various speciality groups' scores differed significantly only for knowledge (P = 0.024) and the mean of total KAP was significantly different between educational and non-educational hospitals (P < 0.05). As hospital type and physician speciality was related to the KAP concerning MWM, therefore it is recommend that all hospitals should develop appropriate protocols for medical waste management based on the this variables using a participatory process with teamwork and continuous training.