Abstract: Since oxidative stress markers are increased in Organophosphates (OPs) toxicity, the efficacy of the antioxidant N-acetyl-L-cysteine (NAC) as an adjunct therapy to atropine and pralidoxime for acute OPs toxicity was evaluated. Twenty-four adult subjects with acute OP toxicity were included in a randomized single blind controlled trial on the use of intravenous NAC. Among included subjects, twelve were randomized to receive NAC and the rest did not receive NAC. The results showed that the needing to atropine but not pralidoxime was reduced in NAC group. The duration of hospitalization was reduced in the NAC group. Addition of NAC to current treatment protocol of acute OPs poisoning is recommended.