African Indigenous Vegetables (AIVs) are integral to traditional diets, providing resilience against climatic challenges while delivering essential nutritional benefits. Nonetheless, their production and consumption are hindered by several barriers, including the limited access to high-quality seeds, insufficient agronomic knowledge, challenges relating to disease and post-harvest management, and fragmented market structures. This study evaluated eight amaranth (Amaranthus spp.) lines for their agronomic performance and analysed the nutritional composition of three species, Amaranthus cruentus, Amaranthus hypochondriacus, and Amaranthus spinosus, as well as their respective plant parts (leaves and seeds). Field trials were conducted utilising a randomised complete block design with three replications, during which parameters such as plant height, disease infestation, leaf count, biomass (both fresh and dry), and 1000-seed weight were assessed. Nutritional analyses were performed following AOAC and ISO-approved food analysis standards. Statistically significant differences (p < 0.005) were observed across the measured traits. The line GR326 exhibited the tallest plant height (112 cm), whereas GR3802 recorded the highest fresh (125,199 kg/ha) and dry biomasses (34,005 kg/ha). A nutritional analysis indicated a higher protein content in leaves (27.96 ± 0.72% in A. Cruentus), as well as notable levels of ash (19.04 ± 0.00% in A. cruentus), calcium (4.27 ± 0.61% in A. hypochondriacus), and potassium (3.80 ± 0.43% in A. spinosus). The seeds demonstrated relatively high fat (5.65 ± 0.81% in A. Spinosus) and fiber (20.05 ± 1.11%) contents. The iron concentration was highest in A. cruentus leaves (2515.64 ± 8.73 mg/g), as were the zinc levels (79.75 ± 8.38 mg/g). These findings highlight the agronomic and nutritional potential of amaranth lines for both vegetable and grain applications. The results suggest that AIVs possess significant potential to mitigate dietary deficiencies, enhance food and nutrition security, and support climate adaptation strategies in Zimbabwe and beyond.