Abstract Canine adenovirus (CAdV), a non‐enveloped, linear dsDNA virus, is a member of the genus Mastadenovirus of the family Adenoviridae. Two different serotypes of CAdVs, canine adenovirus type 1 (CAdV‐1), which causes infectious canine hepatitis (ICH), and canine adenovirus type 2 (CAdV‐2), which causes canine infectious laryngotracheitis, have been identified in dogs. In this report, we discuss a case of fatal CAdV‐1 infection in a 4‐month‐old, male, unvaccinated, Rajapalayam breed dog. Postmortem examination results were suggestive of CAdV‐1 infection, which was confirmed by histopathological examination, molecular characterisation and phylogenetic analysis. Sequence analysis of the CAdV‐1 strain showed a close similarity with the Australasian‐Europe cluster, a high identity (99.78% nucleotide and 98.91% amino acid identities) with a CAdV‐1 isolate (KU75571) from a fox in the United Kingdom, and a unique substitution (W126S) in the E3 protein encoding sequence.