Mango is a major fruit crop of the tropical and subtropical regions of the world. There are numerous mango cultivars being cultivated around the world including in the southern Arabian Peninsula. The diversity of mango cultivars in Oman has not been studied and the majority of mango trees remain unidentified. We investigated the morphological diversity of mango cultivars grown in Oman. Quantitative and qualitative characteristics of imported mango cultivars, locally grown cultivars, and surveyed unknown mango cultivars were compared using multivariate analysis and analysis of variance. Shanon-Weaver diversity index (H') showed large phenotypic diversity in mangoes cultivated in Oman, particularly in the quantitative characteristics of the fruits. Identification of unknown cultivars was possible using UPGMA pairwise-comparison of the phenotypic characteristics with that of known cultivars. Mango cultivars from the same region tended to group together. Results from this study will help further studies on the biodiversity of mangoes in Oman and to develop the appropriate breeding program for improving mango cultivars in arid regions.