In the present study, the morphological variation among seventeen accessions from four quinoa populations (Giza 01, Q101, Q102, and Black) cultivated in a semi-arid region of Algeria was investigated using 26 morphological descriptors established by the International Union for the Protection of New Varieties of Plants (UPOV), along with descriptors from FAO, PROINPA, INIAF, and FIDA. The study aimed to determine which of these descriptors serve as robust estimators of phenotypic diversity within quinoa populations accessions and to analyze the patterns of morphological diversity in cultivated quinoa in Algeria. To address these objectives, Principal Component Analysis (PCA), Hierarchical Cluster Analysis, and the Shannon–Weaver diversity index (H’) were employed. The selected 26 descriptors covered plant structural traits, leaf characteristics, inflorescence features, stem properties, panicle attributes, and seed traits to assess the overall degree of polymorphism among the studied accessions. The computed H’ index values ranged from 0.38 for plant height (PH) to a maximum of 0.98 for branching type (TB), leaf size, and foliage color (FC). The average diversity index among all traits and populations was 0.59, reflecting a substantial level of genetic diversity within the collection. The relative magnitude of the first two PCA eigenvectors indicated that 11 out of the 26 descriptors were the most significant for populations classification. Multivariate analyses, including factorial correspondence analysis and cluster analysis based on morphological descriptors, facilitated the classification of the quinoa accessions into three discrete groups. The first group consisted of four accessions (Giza 01), while the second group was subdivided into two subgroups: the first, a major subgroup comprising eight accessions (Q102), and the second, a minor subgroup with a single accession (Q101). The third group included four accessions (Black). The findings of this study represent a crucial step toward the efficient selection of promising quinoa accessions and their optimal management and conservation.