Back ground: over the past decade, elderly population has increased dramatically. Hence, age associated disease like osteoporosis has become a major public health problem. Osteoporosis is one of the major causes of disability, morbidity and mortality in older people, also it has an impact on elderly quality of life. Aim of current study was to assess knowledge and health behavior of osteoporotic elderly regarding osteoporosis. Design: A descriptive cross section design was used to carry out the current study. Setting: The present study was conducted at orthopedic outpatient clinic in Zagazig University hospitals. Sample: a purposive sample of 429 elderly patients with osteoporosis were participated. Tools: A structured interview questionnaire composed of five parts was used, covering demographic characteristics, medical and family history, knowledge, practice of healthy behaviors, and activities of daily living of elders with osteoporosis. Results: the results of the present study revealed that the majority of elderly with osteoporosis had concomitant chronic disease. Osteoporosis occurred gradually and mainly manifested by low back pain (83.9%). Considering activities of daily living, 39.4% of elderly were fully independent. Although 93.9% of elderly had satisfactory knowledge level regarding osteoporosis, 97.2% had inadequate health behaviors. Conclusion: Ultimately, being from urban, and the higher the elderly age and education, the better their knowledge and practice of health behavior. Recommendation: encourage people at high risk of osteoporosis specially women to carry out periodic medical examination for early detection to avoid serious consequences, also further researches on larger scale are required