In this study, the SureSelect target enrichment system for Illumina Multiplexed Sequencing was applied to proviral DNA sequencing of bovine leukemia virus (BLV). The complete genomic DNA sequences of four Vietnamese BLV strains were successfully obtained with high read depth values and a genome coverage of 100% across all sequenced samples, in less than one week. This study provides the first complete Vietnamese BLV genome sequences. Their genetic variability and phylogenetic relationship were also analyzed and compared with those of 28 whole BLV genome sequences from different parts of the world. The results obtained provided new insights into the genetic diversity of the BLV tax gene, and further enabled us to identify nucleotide mutations in the gene that might not have been detected with the commercial detection kit that is currently available.