African swine fever (ASF) continues to spread, threatening the global swine industry and endangered swine species. Sri Lanka is a tropical island situated south of India in the Indian Ocean. Here, we report the first detection of ASF in Sri Lanka. In September 2024, increased pig mortality was reported across the country, with initial confirmation of porcine reproductive and respiratory syndrome (PRRS). Despite vaccination for PRRS, the mortalities continued to increase and therefore, tissue samples collected from dead pigs were subjected to ASF real-time PCR. ASFV genomic material was detected in most of the samples. The real-time PCR-positive samples were then subjected to genotyping by partial genome sequencing. All p72 and p54 sequences were found to be aligned with ASFV genotype II viruses, and CD2v sequences were found to be aligned with ASFV serogroup 8 viruses. The real-time PCR-positive samples were inoculated onto primary porcine leukocytes for virus isolation, and a selected number of tissues collected from dead pigs were subjected to histopathology. Histopathological studies revealed widespread loss of lymphocytes together with inflammation and extensive staining of ASFV antigens in tissue samples. Hemadsorption (HAD)-positive isolates were obtained from seven clinical samples, and three of them were subjected to whole-genome sequencing. Phylogeographic analysis of the whole-genome sequences showed that the virus is closely related to ASFV strains circulating in China and Hong Kong.