Psoas abscess is a rare disease in childhood. Usually its diagnosis is diffucult and so delayed. A five-year-old girl was admitted with high fever, sweating, swelling and pain on tight thigh and abdominal pain for one week. On family history there was no contact with any known tuberculosis case. She had two siblings who had died clue to diarrhea and pneumonia. At physical examination, the right leg was tender with movements and in flexion posture. There was also defence and rebaund on abdomen. Ultrasonography revealed a mass lesion at 39x17 mm diameters with heterogenous echo next to the psoas muscle.