Amaranths (Amaranthus sp.) are cosmopolitan and include grain, vegetable, ornamental and weed types. Forteen simple sequence repeat (SSR) markers were used to analyze the genetic diversity of 59 accessions of cultivated amaranth from Asian countries. A total of 63 alleles were detected with an average of 4.5 per locus. The averaged values of gene diversity and polymorphism information content (PIC) were 0.35 and 0.33, respectively. Alleles per locus in accessions from South Asia was 4.35, whereas 2.93 and 3.79 alleles per locus were found in Nepal and India, respectively. The mean gene diversity in Central Asia and East Asia was 0.36 and 0.28, respectively, whereas the mean PIC values were 0.27 and 0.22, respectively. The genetic diversity and PIC of the India amaranths were higher than that of other Asian countries. The model-based structure analysis revealed the presence of three subpopulations, which was basically consistent with clustering based on genetic distance. An AMOVA analysis showed that the between-population component of genetic variance was less than 56.16% in contrast to 43.84% for the within-population component. The overall FST value was 0.56, reflecting genetic differentiation within Asian amaranths. These findings could be used for designing effective breeding programs aimed at broadening the genetic bases of commercially grown varieties.