Psoas abscess in cases of tuberculosis originates from the primary lesion in the lower dorsal or the lumbar spine. From the spinal origin of the Psoas muscle, this abscess tracks down its sheath and may be palpable in the iliac fossa, in the lumbar triangle, in the upper part of thigh below the inguinal ligament. We present a rare case, where patient presented with thigh swelling, which on first look gave an impression of a malignant origin. But subsequent investigation revealed it to be one of tuberculous origin, and that to, tracking down of a Psoas abscess. According to best of our knowledge, there has been no reported case of a Psoas abscess tracking down to the thigh and knee and mimicking a tumour.