Veronica L., the largest genus in the family Plantaginaceae, is widespread in various habitats. Due to their long-blooming flowers, Veronica species have high horticultural value as indoor potted, garden, and landscape plants. Furthermore, Veronica plants are extremely important owing to their notable diversity in habitat usage, ploidy level, and evolution. Several native taxa, which are of key interest in breeding programs and phylogenetic studies, have been identified in Korea. The genome sizes and chromosomal characteristics are basic cytogenetic features of all taxa, and their knowledge is a prerequisite when commencing genome sequencing projects. It can provide essential information for cytogenetic, taxonomic, phylogenetic, and evolutionary studies. Thus, cytogenetic analysis and genome size estimation of seven Veronica taxa native to Korea were conducted in this study. Fluorescence in situ hybridization (FISH) karyotype analysis and chromosome counting was conducted using metaphase chromosomes probed with 5S and 45S rDNA. Nuclear DNA content and genome size were determined using flow cytometry. FISH karyotype analysis revealed a common number of 5S loci and varying 45S signals that create distinctive rDNA distribution patterns in each taxon. The results indicated that the seven investigated Veronica taxa have calculated genome sizes (1C values) ranging from 517.1 to 862.0 Mbp. This study is the first to report the chromosome number and karyomorphology of seven Veronica taxa native to Korea, as well as the use of rDNA markers for identifying individual chromosomes. These findings contribute to the crucial understanding the genomic characteristics of species within the genus Veronica, serve as a basis for studying Veronica phylogeny and evolution, and provide valuable information for future breeding programs.