Thymoma associated with hypogammaglobulinemia and profound susceptibility to recurrent and serious infections was first reported by Good in 1954, after whom it was named as Good's syndrome. Chronic diarrhea associated with thymoma is almost always seen in patients with hypogammaglobulinernia. However, chronic diarrhea in a setting of normal gammaglobulins have been rarely reported. We hereby report two cases of thymoma with normal immune functions, presenting with chronic diarrhea as the only symptom of thymic malignancy. We discussed the etiopathogenic relation between thymic pathology and diarrhea and review the cases of thymoma associated with chronic diarrhea in the English literature.