Postnatal cytomegalovirus enterocolitis is uncommon in immunocompetent infants. We report a 10-week-old term boy with severe and prolonged secretory diarrhea, leading to dependence on total parenteral nutrition and a 10-week hospitalization. Cytomegalovirus enterocolitis was diagnosed based on duodenal biopsy in the context of marked viremia, and the child recovered promptly on initiation of ganciclovir. Collated case reports reveal delayed diagnoses as the norm but rapid improvement with antiviral treatment. Cytomegalovirus enterocolitis should be considered early as a differential diagnosis in infants with refractory diarrhea.