Background: Osteoporosis is a potential metabolic complication of diabetes mellitus (DM). Therefore, patients with DM should have adequate osteoporosis knowledge and beliefs in order to get engaged in osteoporosis preventive behaviors. The objective of this study was to assess osteoporosis knowledge and beliefs among diabetic patients. Methods: This was a cross sectional study carried out at Al-Makhfiah governmental primary healthcare unit in Nablus, Palestine from September 2016 to December 2016. The tools used to assess knowledge and beliefs were Osteoporosis Health Belief Scale (OHBS) and the Osteoporosis Knowledge Test (OKT) respectively. Results: Three hundred diabetic patients were interviewed regarding their knowledge and belief about osteoporosis. The study sample included 192 (64.0%) females. Mean ± standard deviation (SD) of the participants was 58.5 ± 9.3 years. Regarding co-morbidities, 229 (76.3%) had at least one co-morbidity other than DM. The majority of participants incorrectly answered 19 out of 32 questions of OKT scale. The mean OKT score was 13.5 ± 4.2 indicating poor osteoporosis - related knowledge. Females had significantly higher nutrition (p = 0.037), exercise (p = 0.043), and OKT score (p = 0.021) than males. Regarding OHBS, female participants had significantly higher belief score of susceptibility (p < 0.01) and seriousness (p < 0.01) of osteoporosis compared to males. Conclusions: Diabetic patients had poor osteoporosis knowledge and moderate perception of susceptibility and seriousness of osteoporosis. These results require implementation of awareness programs among DM patients to increase their practices regarding preventive measures of osteoporosis such as calcium intake and exercise. © 2018 The Author(s).