The pygmy hog is a rare, small and highly endangered mammal belonging to the Suidae family, and it is presently found only in the Assam state of India. While investigating the cause of death of pygmy hogs housed at a conservation centre for captive breeding and research at Basistha, Assam, it was confirmed that they were susceptible to and died as a result of contracting classical swine fever (CSF), caused by CSF virus (CSFV), which is a highly infectious endemic disease of domestic pigs in India. The post-mortem findings and serum CSFV-specific antibody titres, along with the isolation of CSFV from two pygmy hogs, and further confirmation by CSFV genomic E2 and 5’ untranslated region (UTR) gene amplification in PCR (polymerase chain reaction), clearly established the cause of death of the pygmy hogs. Further, on phylogenetic analysis, the pygmy hog CSFV 5’ UTR sequences were grouped in the genotype 1.1 cluster of Indian CSFVs, and hence the strains causing infection were closely related to CSFV isolates circulating in domestic pigs. Therefore, the occurrence of CSF in this endangered species may pose a potent threat to their existence unless properly controlled, and thus it needs urgent attention. To the authors’ knowledge this is the first report on CSF in pygmy hogs.