BACKGROUND Gastrointestinal (GI) polyposis is a rare condition in GI diseases. To date about 500 cases of Cronkhite-Canada syndrome (CCS) have been reported worldwide. CASE SUMMARY We report a 60-year-old female patient who presented with dyspepsia, abdominal pain, and weight loss of 1-year duration. Her physical examination showed alopecia and onychodystrophy. Upper endoscopy revealed diffuse markedly thickened gastric mucosa involving the whole stomach with thickened gastric rugae and numerous polypoidal lesions. Histopathological examination showed marked hyperplasia of the foveolar glands with inflammatory cell infiltration. Endoscopic ultrasound showed a significantly hypertrophic mucosa and muscularis mucosa, while the submucosa and the muscularis propria were spared, favouring its benign nature. Colonoscopy showed multiple sessile polyps scattered at different parts of the colon. Histopathological examination revealed tubular adenomatous polyps with low-grade dysplasia. Differential diagnoses included CCS, Menterier disease (MD), other polyposis syndromes, lymphoma, amyloidosis, and gastric malignancies. The presence of alopecia, nail dystrophy, GI polyposis, markedly thickened gastric mucosa and folds, abdominal pain, weight loss, and marked foveolar gland hyperplasia; all was in favour of CCS. Lymphoma was excluded due to sparing of the muscularis propria. The presence of colonic polyps and antral and duodenal infiltration, and the absence of hypoproteinaemia decreased the possibility for MD. CONCLUSION The patient was diagnosed as having CCS.