Filarial infection is an important disease in human and animal medicine. Several ¿larial worms are of importance, especially nematodes in the Onchocercidae. The Asian elephant (Elephas maximus) is an endangered animal and is very important from several socio-economic and ecological aspects in Thailand. Various parasites can be found in elephants; however, data related to ¿larial infections in elephants is limited. The objective of this study was to detect ¿laria in the blood of Asian elephants in Thailand, based on a polymerase chain reaction (PCR) technique. Blood samples were collected from 208 Asian elephants and detected for ¿laria using PCR, targeting the region of the internal transcribed spacer 2 (ITS2), the cytochrome c oxidase subunit 1 (cox1), and the RNA polymerase II large subunit (rbp1). In total, 4.33% (9 out of 208) of the sampled elephants had Loxodonto¿laria spp. DNA with 100% query coverage. In addition, the obtained cox1 and rbp1 sequences matched with Loxodonto¿laria sp., Onchocerca sp., and Diro¿laria sp. There were no identi¿ed risk factors (sex, age, location, and packed cell volume) related to Loxodonto¿laria infection in elephants. The analyses of the phylogeny of ITS2 sequences demonstrated that the Loxodoto¿laria-positive sequences were closely related to Onchocerca dewittei japonica and Onchocerca dewittei dewittei with 100% query coverage. Notably, the concatenated phylogenetic trees of ITS2 and the cox1 and rbp1 genes were closely similar to Loxodonto¿laria sp. To describe in detail the genomic DNA of Loxodonto¿laria spp., other genes should be additionally studied using a more discriminatory technique, such as DNA barcoding or whole genome sequencing.