Osteopetrosis is a rare hereditary disease that was first described by a German Albert Schonberg in 1904. At least five types of osteopetrosis have been described. Among them osteopetrosis congenita (autosomal recessive) and osteopetrosis tarda (autosomal dominant) are most common. Here we are reporting a case of osteopetrosis tarda, who is a female of fifty years of age presented with fracture femur. Preoperatively there was no suspicion of osteopetrosis. She was only suspected while introducing an IM Nail during her fracture reduction. Diagnosis of osteopetrosis was confirmed post operatively by histopathology of medullary cavity of her femur.