Objective: To investigate the effects of cyclooxygenase (COX) inhibitors including celecoxib, indomethacin, and nimesulide on postoperative adhesion formation. Material and Methods: Forty-eight female Wistar-Albino rats were randomly divided into four groups: control (saline solution), celecoxib, indomethacin, and nimesulide groups. The uterine horns of rats were traumatized with unipolar electrocautery. Drugs of each group and saline in the control group were insillated on travmatized areas of horns as intraperitoneally. After three weeks, the extent and severity of adhesions with a standardized scoring system were evaluated. Results: The extent and severity of postoperative adhesions were significantly reduced in nimesulide group compared with the control group. The extent but not severity of adhesions in rats given indomethacin was significantly reduced. Celecoxib showed no significant reduction in the extent and severity of adhesions. Conclusion: Nimesulide is more effective than the other COX inhibitors in the prevention of postoperative adhesions in rats.