Paraquat poisoning is a fatal type of herbicide intoxication. It is characterized by multi-organ failure and pulmonary fibrosis with respiratory failure. Intravenous and intramuscular injection of paraquat is rarely described. However, We encountered two fatal cases of acute poisoning caused by paraquat injection. Two patients were admitted to our emergency unit after intravenous and intramuscular injection of 23.8% paraquat (about 476 mg of paraquat). A 37-year-old man diluted 2 ml of 23.8% paraquat solution with 1 ml of normal saline and injected it both intravenously into his left antecubital fossa and intramuscularly into his abdomen in a suicide attempt. He died 5 days later from respiratory failure and acute renal failure. A 92-year-old man was injected intravenously into his right antecubital fossa by his grandson with 2 ml of 23.8% paraquat solution diluted with 1 ml of normal saline. He died 2 days later from early circulatory collapse and multi-organ failure (metabolic acidosis, acute renal failure, coagulopathy). Intravenous and intramuscular injection with a small quantity of paraquat resulted in fatal toxicity in our patients.