Fetal hydrops associated with neonatal tumours is an uncommon occurrence. The diagnosis can be established prenatally by ultrasound examination. The treatment of choice is surgery which may be curative. We report the case of a male born at 32 weeks gestation who presented with severe hydrops fetalis and a thoracic mass. The child could not be operated upon because of rapid clinical deterioration. The autopsy findings confirmed the diagnosis of congenital fibrosarcoma. This is, to our knowledge, the first case of hydrops fetalis associated with fibrosarcoma. Conclusion The association of hydrops fetalis and fibrosarcoma is an exceptional observation but can be added to the long list of differential diagnoses of non-immune hydrops.