Modified choledochoduodenostomy and gastrojejunostomy were used successfully to treat extensive duodenal ulceration and perforation in a dog. Concomitant pyometra, simultaneously managed by ovariohysterectomy, may have predisposed the dog to stress ulceration. Choledochoduodenostomy was performed by transplantation of the entire common bile duct and associated major duodenal papilla to a more distal duodenal location. An indwelling choledochostomy tube was used to stent the anastomotic site, externally divert bile flow, and allow postoperative cholangiography. Early postoperative complications included presumed metronidazole-induced neurotoxicosis, choledochostomy tube obstruction, and pancreatitis, all of which resolved within 2 weeks. The dog was clinically normal and medication (ranitidine and sucralfate) was discontinued 35 months later.