Pearson syndrome (PS) is a rare mitochondrial disorder characterized by sideroblastic anemia and exocrine pancreas deficiency as a result of mitochondrial DNA deletion or deletion-duplication. A 21-year-old woman and 11-year-old brother who had been diagnosed as PS at the age of 18 and 8, respectively, were admitted to our hospital with the complaints of chronic diarrhea while using exogenous pancreas enzymes. Diarrhea was present in both for a long time and attributed to existing PS. Endoscopic and laboratory examinations revealed celiac disease (CD). After gluten-free diet, their symptoms were resolved. Detailed family investigation revealed that parents and the sister of the siblings were free of both PS and CD. To our knowledge, there has been no previous report of the presence of these 2 disorders, PS and CD, in the same patient. CD should be screened and treated appropriately in cases with PS.