African swine fever (ASF) is a highly infectious disease of pigs caused by African swine fever virus (ASFV). In order to identify potential genetic variations among ASFV strains circulating in Vietnam, 26 ASFV isolates from organs and blood samples collected from domestic pigs from 23 different provinces of northern, central and southern Vietnam during 2019-2020 ASF outbreaks were genetically characterized. Nucleotide sequences were determined for a portion of the B646L (p72) gene, the complete E183L (p54) gene, the variable region of EP402R (CD2v), the central variable region (CVR) of pB602L, and a tandem repeat sequence (TRS) between the I73R and I329L genes. Analysis of the partial B646L (p72) and EP402R (CD2v) gene sequences and the full-length E183L (p54) gene sequence showed that all 26 ASFV isolates belonged to genotype II and serotype VIII and that they were identical to the strain Georgia/2007/1 and all ASFV strains sequenced in China. The TRS between the I73R and I329L genes contained a 10-nucleotide insertion that was observed in the Chinese ASFV strain CN201801 isolated from domestic pigs in 2018, but not in the Georgia/2007/1 and China/Jilin/2018/boar strains isolated from wild boar in China. This is the first intra-epidemic genome analysis reported for the ASFV strains circulating in Vietnam.