Genome sequencing and analysis of snake adenovirus type 1 (SnAdV-1), originating from corn snake, were completed. This is the first full genomic sequence of an adenovirus from reptilian hosts. The presence of characteristic genus-common genes and transcription units, showed that SnAdV-1 shares similar genome organisation with members of the recently established genus Atadenovirus. Three novel open reading frames of yet unknown functions were found. One of these seemed to be related to a putative gene, the so-called 105R that has recently been described from the genome of the tree shrew adenovirus. The other two putative genes were found to be unique for SnAdV-1. On phylogenetic trees, SnAdV-1 clustered within the atadenovirus clade. Thereby the hypothesis on the reptilian origin of atadenoviruses was further strengthened. Interestingly, however, one of the most striking features of atadenoviruses, namely the base content heavily biased towards A+T, is not characteristic for SnAdV-1 having a genome of balanced composition with a G+C value of 50.21%.