Nosocomial viral infections account for at least 5% of the total of NI and reach 23% in pediatric wards. The nosocomial infection (NI) incidence rate varies from 0.59 to 0.72 per 100 patients in pediatric wards. Many viruses have been associated with NI in pediatric wards. Rotavirus and respiratory syncytial virus (RSV) are the most frequent. Other viruses frequently identified are: calicivirus, adenovirus, astrovirus, influenza et para-influenza, rhinovirus and coronavirus. Asymptomatic infections occur frequently. The period of communicability varies and depends on the virus. It often begins before the clinical signs appear and ends after the healing. Viral shedding may be intermittent. Children and hospital environment and less frequently hospital staff are the main source for the virus. Poor handwashing results in direct spread to patient or self-inoculation even for respiratory viruses like RSV and rhinovirus. The main risk factors for NI are prolonged hospital stay, past history of prematurity and low age. Immunocompromised patients constitute a special high-risk group. Understaffing is also a risk factor. Minimal infective doses depend on the route of inoculation and the kind of virus. Low doses are for example sufficient for rotavirus, adenovirus and calicivirus. Viral inactivation is all the more easy when there is an envelope. Handwashing and appropriate isolation (technical and geographical) are the mainstay of prevention of viral NI. Vaccines are promising, especially for rotavirus.