An eight year-old intact male Irish setter was admitted to the emergency service for evaluation of vomiting, hematemesis, pyrexia, and lethargy. The diagnosis based on clinical signs, barium study, abdominal sonogram, upper endoscopy, biopsy and histopathology was a gastric adenocarcinoma with severe inflammation and ulceration of the gastric mucosa. The dog was treated with conventional therapy including ampicillin, enrofloxacin, amoxicillin with clavulanic acid, famotidine, metoclopramide, and sucralfate and Oriental Medicine (OM) therapy including acupuncture and Korean herbal therapy. The disease pattern identification based on OM theory was Ban Wei or Yeol Guk (stomach cancer) caused by Phlegm-Heat accumulation with Blood stasis in the Middle Jiao. Two sessions of acupuncture treatment and 120 days of the Korean herbal formula Modified Chi Am Tang (Jia Wei Zhi An Tang) over a 10 month period were provided. A second upper endoscopy, performed after 2 months of herbal therapy, showed no signs of an ulcer or inflammation in the stomach and the tumor size was significantly reduced. Minor edematous, erosive and ulcerated lesions were found in the duodenum. There was no remarkable clinical manifestation and the Karnofsky performance score was 90-95 (scale 0-100) after 120 days of herbal therapy. The dog is still alive and doing well 4 years after the original diagnosis. This report demonstrates how the correct herbal therapy may be useful in supporting patients with cancer.