Painful preperitoneal collection is a rare complication following endoscopic totally extraperitoneal inguinal hemioplasty. Here we present the case of a woman who underwent endoscopic extraperitoneal inguinal hernioplasty for a left inguinal hernia. Her past health was good. During the dissection of the extraperitoneal space, clear ascitic fluid was noted upon breaching the peritoneum near the round ligament. Endoscopic stapling was used to close the peritoneal tear, and the procedure was completed uneventfully. The patient complained of left iliac pain after the operation. A physical examination showed no swelling over the left iliac fossa. Contrast computed tomography of the abdomen revealed preperitoneal fluid collection over the hernioplasty site and a small amount of ascites. Expectant treatment with pain control by oral analgesics was adopted. A follow-up CT scan 4 months after the operation showed resolution of the preperitoneal fluid collection but with increased ascites. Abdominal paracentesis with peritoneal fluid for cytology analysis found adenocarcinoma cells. The patient succumbed to a terminal malignancy a year after surgery. Conversion of endoscopic extraperitoneal inguinal hernioplasty to open repair should be considered upon intraoperative discovery of ascites. Painful preperitoneal collection is a possible sequela following endoscopic extraperitoneal hernioplasty in patients with malignant ascites.