A 6-month-old male miniature pinscher dog developed chronic ascites, formation of fibrous membrane covering the abdominal organs, and numerous adhesions between the intestinal loops. The membrane and adhesions were surgically removed twice, but the dog died 1 month after initial presentation. Necropsy revealed recurrence of the membrane and intestinal adhesions. The fibrous membrane was composed of a thick layer of mature collagenous connective tissue, covered by immature collagenous connective tissue with mild lymphoplasmacytic infiltration, prominent neovascularization, and fibrin exudation. Similar fibrotic lesions were observed in the serosa of the liver, spleen, stomach and intestines. These findings are consistent with encapsulating peritoneal fibrosis reported in humans and dogs. The dog also had a maldeveloped liver, which is characterized by disorganized hepatic lobules and disarranged hepatic cords.