A collection of thirty argan trees (Argania spinosa (L.) Skeels), representing the Aoulouz provenance in southwest of Morocco were used to study genetic variability and selection for three years. In this study, the genetic diversity of thirty genotypes (tree mothers) of argan (Argania spinosa) collected from Aoulouz was evaluated using agro-morphological characters. The main objective of the study was to assess and describe with multivariate analysis the genetic diversity in order to select good candidate trees for a future breeding program. The results obtained showed a large variation for all the traits examined. Analysis of variance using general linear model provided a significant variation between genotypes. Furthermore, genotypic and phenotypic variances for quantitative traits, particularly for seed length, seed width, almond length and oil content were higher. Phenotypic coefficient of variation was higher than genotypic coefficient of variation for all the characters. High heritability was recorded for oil content (97.90%), seed width (72.68%) and seed length (57.55%) respectively, indicating the additive gene action. In addition, a three dimensional plot based on principal coordinate analysis method was used to evaluate the performance genotypes as to the production of oil for three years. The genotypes ‘Ao-12R’, ‘Ao-7R’, ‘Ao-4R’, ‘Ao-4V’, ‘Ao-11R’, ‘Ao-8V’ and ‘Ao-7V’ were found to be the best for high oil content. Identification and selection with superior agronomic traits may be an effective method for genetic improvement of argan trees, and a first step for further breeding studies.