A 3-year-old boy presented with persistent abdominal pain, hematuria and facial pallor with progressive anemia. A computed tomography scan showed a massive intraperitoneal hemorrhage and tumor mass in the bladder. Histological examinations of the resected tumor revealed findings of pseudosarcomatous myofibroblastic tumor (PMT). The clinico-pathological features of this case warn us that PMT can cause acute abdomen syndrome with massive intraperitoneal hemorrhage.