Cyprinid herpesvirus 3 (CyHV-3) is the causative agent of koi herpesvirus disease and poses a significant threat to common and koi carp. Since its first description, the virus has spread worldwide. In 2010 and 2011, mass mortality of common carp was reported in a hatchery and several ponds in northern Vietnam. CyHV-3 was detected in infected tissues by PCR, confirmed by sequencing of the thymidine kinase gene. Duplex PCR demonstrated that the virus belonged to the genetic lineage (I++/II-) previously described in Indonesia. This suggests CyHV-3 as the causative agent of the disease outbreak and constitute the first report of CyHV-3 in Vietnam.