Amaranths are a type of plant that belongs to the NAD-malic enzyme-type C4 metabolism category. They have a unique C4 anatomy, which is present in their bracts, cotyledons, and leaves. This allows them to produce food through the C4 photosynthetic pathway and rapidly adapt to unfavorable environmental conditions. In this study, 120 amaranth genotypes were evaluated for physio-morphological traits, genetic variability, and growth performance assessment from Ethiopia. The results of the analysis of variance showed that all examined physio- morphological parameters, except the rate of photosynthesis and stomata conductance, had mean squares that varied considerably (P < 0.001) owing to genotypes. The estimates of genetic variability, heritability, and ex- pected genetic advance indicated an incredible extent of genetic diversity among amaranth genotypes, with a significant selection pressure for these traits in the population to produce better genotypes for improved amaranth. Selection based on desirable features such as leaf-to-air vapor pressure deficit, transpiration rate, chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, leaf area, plant height, leaf number, and root weight can be useful in achieving the intended genetic gains for improvement since these traits appear to be more controlled by additive gene activity. Thus, selection in amaranth genotypes may consider these desired yield- related features. Moreover, the study showed that certain genotypes (ALE-073) exhibited better intercellular CO2 concentration (Ci), leaf-to-air vapor pressure deficit (VPD), transpiration rate (E), and leaf number (LN), resulting in better grain yield. Understanding the relationship between LA and E can help in selecting crops for high E and may provide an avenue to improve leaf yield. Furthermore, some of the selected genotypes in this study could be used as potential parents for improving the genetic gain in amaranth breeding programs. The study concluded that there was additive gene action present since the Ch a, Ch b, TCh, and Tca markers exhibited 100 % heritability. This showed that the use of these characteristics for selection, which indicated a potentially exploitable variation, would be more effective and successful in the long run in breeding programs than the use of other traits for splitting generations.