Severe electrolyte disturbances caused by fish poisoning are rarely reported in the literature. We present an unusual outbreak of palytoxin poisoning associated with the consumption of Goldspot herring (Herklotsichthys quadrimaculatus). Four family members became ill after eating 2 species of marine fish. The presenting symptoms and signs included bitter taste, oral numbness, nausea, vomiting, abdominal pain, and hypertension, which were followed by myalgia, limb numbness, sensorimotor polyneuropathy, and abnormal cold and warm sensations. The index case manifested hyperkalemia, hyperphosphatemia, and acute kidney injury, and developed severe cardiac dysrhythmias. He died 21 hours postingestion. Palytoxin and related compounds were identified by liquid chromatography tandem mass spectrometry in one of the leftover fish. Palytoxin poisoning is rarely reported and is difficult to diagnose in the absence of laboratory confirmation. Palytoxin poisoning should be considered in patients who manifest hyperkalemia and hyperphosphatemia after the consumption of marine fish, and timely laboratory analysis should be sought.