Background: We present two patients who suffered from endometritis as a result of a foreign body reaction to an anti-adhesive barrier positioned during hysteroscopic surgery. Case: The first case—who had previously undergone hysteroscopic lysis of intrauterine adhesions—presented with persistent abdominal pain and vaginal discharge. Ultrasound revealed an irregularly shaped strip of hyperechoic lesion. On diagnostic hysteroscopy, a foreign body presenting as a flattened bundle was observed and identified as the anti-adhesive barrier positioned during her previous surgery. The second patient—who had previously undergone laparoscopic surgery and hysteroscopic polypectomy—presented with abdominal pain in the left lower quadrant. Ultrasound revealed an intrauterine hyperechoic avascular lesion, while hysteroscopy identified a piece of crumpled plastic wrap. Both patients showed clinical improvement after removal of the extraneous material. Conclusion: Intrauterine positioning of anti-adhesive barriers during hysteroscopic surgery can give rise to endometritis as a result of foreign body reactions.