BACKGROUND Hexaflumuron is a benzoyl urea pesticide widely used in agriculture. This is the first case of severe toxicity of hexaflumuron. METHODS A 51-year-old man was admitted to the poisoning ward of the Emam-Reza Hospital for loss of consciousness and hypotension secondary to pesticide toxicity. He had metabolic acidosis, bradycardia, and diffuse erythematous skin color change in the abdomen and legs. The results of toxicology tests were negative except positive test result for tricyclic antidepressants in immunochromatographic assay of urine. He was treated with normal saline, norepinephrine infusion and bicarbonate. His intoxication finally resulted to cardiac arrest and death on the 4th day of hospitalization, secondary to septic shock. CONCLUSIONS Acute poisoning with hexaflumuron can be life-threatening, thought its LD50 is greater than 5000 mg/kg. It may change the patient's skin color to cherry and cause hypotension, loss of consciousness and metabolic acidosis, however, conclusive evidence to support these assumptions are required.