Snakehead fishes of the family Channidae are obligatory air-breathers freshwater predators, the vast majority of which belong to the genus Scopoli, 1777. species are characterized by high karyotypic diversity due to various types of chromosomal rearrangements. It is assumed that, in addition to the lifestyle, fragmentation and isolation of snakehead populations contribute to an increase in karyotypic diversity. However, the chromosome complements of many isolated populations of widespread species remain unknown, and the direction of karyotype transformations is poorly understood. This paper describes the previously unstudied karyotypes of (Cuvier, 1831) and (Bloch, 1793) from Phu Quoc Island and analyzes the trends of karyotypic evolution in the genus . In , the karyotypes are differed in the number of chromosome arms (2n = 48, NF = 50 and 51), while in , the karyotypes are differed in the diploid chromosome number (2n = 44 and 43, NF = 48). A comparative cytogenetic analysis showed that the main trend of karyotypic evolution of species is associated with a decrease in the number of chromosomes and an increase in the number of chromosome arms, mainly due to fusions and pericentric inversions. The data obtained support the assumption that fragmentation and isolation of populations, especially of continental islands, contribute to the karyotypic diversification of snakeheads and are of interest for further cytogenetic studies of Channidae.