In the past two decades, there has been a rapid increase in the number of organ transplanted worldwide, including Brazil, along with an improvement in survival and quality of life of the transplant recipients. Osteoporosis and a high incidence of fragility fractures have emerged as a complication of organ transplantation. Many factors contribute to the pathogenesis of osteoporosis following organ transplantation. In addition, most patients have some form of bone disease prior to transplantation, which is usually related to adverse effects of end-stage organ failure on the skeleton. This chapter reviews the mechanisms of bone loss that occur both in the early and late post-transplant periods, as well as the features specific to bone loss after kidney, lung, liver, cardiac and bone marrow transplantation. Prevention and treatment for osteoporosis should be instituted prior and in the early and late phase after transplantation, and will also be addressed in this article.