Khamnigan is a poorly documented and endangered Mongolic language. This study examines basic word lists from eight Khamnigan communities in China, Mongolia and Russia, revealing strong lexical similarities indicative of dialectal variation within a single language. Specific affinities were found between certain pairs of communities, with the China variety closely related to Tarbaljei and Mogoitui (in Russia), the Mongolian Bayan-Uul variety to Dadal (in Mongolia) and Tarbaljei (in Russia), and the Tarbaljei variety to Mogoitui (in Russia). Lexical analysis places Khamnigan in the Northern Mongolic subgroup, with a division into the Buriad-Khamnigan and Mongol-Oirat-Ordos-Barga clusters. Geographical patterns suggest later influences on idiom evelopment, with common lexical innovations linking Khamnigan varieties to neighboring languages: East Buriad, Khalkha, and Old and New Barga.