The genus Ocimum belonging to Lamiaceae is considered as one of the most economical medicinal plants throughout the world. It is used in medicinal tea, and essential oil production, in spices, as vegetable, and also as a pot herb. The aim followed in this study was to evaluate the genetic diversity of 38 native populations collected from different geographical origins of Iran along with two foreign breed cultivars (Opal and Keshkeni Luvelou) as control. A number of 32 field conditions qualitative and quantitative morphological traits were taken into account. Taxonomic studies revealed that the samples belonged to 3 species of: O. ciliatum (23 populations), O. minimum (1population), O. basilicum (15 populations). According to analysis of variance highly significant differences were observed among the populations. Duncan’s Multiple Range Tests indicated that the accessions were significantly different in all the evaluated parameters. The highest plant height (49/5 cm) and inflorescence whorl number (11/3) were obtained from population 24, while the highest inflorescence heights obtained from accessions 6 and 13 (15/1 cm). The accessions 4 and 5 benefited from the highest leaf dimentions of length and width.