<p>Amaranthus includes over 60 species and has been extensively studied for its adaptability to various climatic conditions. This study evaluated the yield performance and stability, and genotype-by-environment (G×E) interaction of three <i>A. cruentus</i> and five <i>A. hypochondriacus</i> genotypes across four environments in central Chile, produced by two locations and two sowing dates. A combined analysis of variance, AMMI, GGE biplot, principal components, and path analysis were employed to analyze the effects of genotype, environment, and their interaction on seed yield and its components. Results revealed that seed yield variability was primarily explained by the kernel number per square meter (<i>r</i> = 0.97), followed by the HI, while aboveground biomass and phenology were less influential. <i>A. cruentus</i> genotypes, particularly CB-01, Benito, and Amaranteca, demonstrated higher seed yield and yield stability, so they were considered broadly adapted genotypes, whereas <i>A. hypochondriacus</i> genotypes exhibited greater sensitivity to environmental changes, especially photoperiod. Revancha emerged as an exception, showing similar behavior to <i>A. cruentus</i>. Early sowing dates delayed reproductive development and negatively impacted seed yield due to photothermal mismatch. Path analysis confirmed differential seed yield formation pathway between species. These findings underscore the necessity of matching genotype phenology with local environmental conditions and support the inclusion of <i>A. cruentus</i> genotypes in cultivation and breeding programs targeting Mediterranean environments.</p>