Background: Recent data from coronavirus disease 2019 (COVID-19) confirm that diabetes, along with advanced age, is an important risk factor for adverse prognosis. Therefore, the present study aimed to determine the status of COVID-19 prevention behaviors and related beliefs among diabetic patients in Hamadan province using protection motivation theory (PMT). Methods: This cross-sectional descriptive study was conducted from April to September 2020. The research population included all diabetics, of whom 355 patients, who referred to an adult endocrinologist in Hamadan, were selected using the convenience sampling method. The data collection tool was a researcher-made questionnaire with demographic variables and PMT constructs. Data were analyzed by SPSS 22 using descriptive statistics, correlation, and logistic regression. Results: According to the result, the PMT construct explained 15% of the variance in the frequency of the intention to perform preventive behaviors. Perceived sensitivity (β=-0.128), perceived response efficiency (β=0.140), and perceived response cost (β=0.386) were the best significant predictors of behavior (P<0.05). There was a significant relationship between gender (P<0.001), marital status (P<0.001), and level of education (P=0.040) in observing preventive behaviors. Conclusion: It is necessary to enhance the levels of awareness and self-efficacy of diabetic patients to reduce fear in this at-risk group. Further, it is appropriate to use PMT to promote preventive behaviors.