We report a case of urinary bladder actinomycosis in childhood. In children abdominal actinomycosis is rare and unlikely involves the urinary tract, so it is often misdiagnosed. An 7-year-old boy was referred to a secondary level hospital because of abdominal pain and dysuria. Physical examination revealed a left hypochondrial mass. Hypothesizing a pelvic rhabdomyosarcoma, a biopsy with mini-laparotomy access was performed. The first histopathological analysis did not show any malignant cells, and a 14-day antibiotic course was ineffective.