Background Cases of cytomegalovirus colitis are exceptionally reported in immuno-competent infant. The pathogenesis is uncertain but breast-feeding is considered as a main source of postnatal infection. Case Presentation Here we report a full-term, formula-fed infant who developed a severe cytomegalovirus anaemia and colitis when aged 2 months. Conclusion Even if the molecular identity between the cytomegalovirus-isolate of the infant and the maternal virus could not be demonstrated, we confirmed through laboratory investigation that cytomegalovirus infection was acquired postnatally. However, the source of cytomegalovirus infection remained unclear. Alternative modes of cytomegalovirus transmission are discussed.