Rehabilitation and release of wild birds hinge upon a comprehensive understanding of both biologic and nonbiologic factors, including the medical and physical fitness of the animal. The objectives of this study were to determine reference intervals of packed cell volume and plasma chemistry values for healthy Eurasian Eagle Owls (Bubo bubo) and to compare blood values between age and sex classes. There were significant differences between males and females in total protein and globulin mean values, with males having higher values than females. Adult and juvenile Eagle Owls differed significantly in the mean values of calcium, alkaline phosphatase, and uric acid, with juveniles having higher values than adults. The calculated reference intervals for Eagle Owls can be used in Eurasian Eagle Owls admitted to rescue centers to assist veterinarians and wildlife managers to clinically evaluate and monitor the health of Eagle Owls and make decisions about when to release them after treatment.