The piriformis muscle originates from the anterior part of sacrum and inserts into the greater trochanter. Then it passes transversely through the greater sciatic foramen via the sciatic notch and inserts on the greater trochanter. It is one of the lateral rotator muscle of the hip & an important land mark in the gluteal region. Since the sciatic nerve descends to the thigh by passing deeper to the piriformis muscles, it is mostly associated with the irritation of nerve which is known as piriformis syndrome. In this study the accessory piriformis muscle was observed in a 59 year-old female cadaver. The abnormality reported in the present study may lead to neurovascular compression syndrome in the upper limb. Knowledge of anatomical variations in the muscular structure and its related neurovascular entrapment is important surgically for orthopaedic surgeons, neurologists and also physiotherapists clinically.