Abstract: The goal of this study is to investigate the effect of preoperative Naproxen on prevention of postoperative pain and analgesic consumption in females undergoing diagnostic laparoscopy. This is a randomized, double-blinded clinical trial. One hundred females (ASA I and II, aged 16-45 years old) scheduled for elective diagnostic laparoscopy under general anesthesia were selected by using a computer generated random list patients and were allocated into two equal groups. The patients received either 1 g Naproxen orally or a placebo tablet 90 min prior to anesthesia. Pain scores were significantly lower in Naproxen group compared with the placebo group, during the first 6 h postoperatively. There was also a significant difference between two groups in the analgesic consumption during 24 h after operation (p = 0.004). Preoperative oral Naproxen in diagnostic laparoscopy is effective for post operative pain relief and reduction of analgesic consumption.