Evaluation of morphological diversity in 144 genotypes of twenty-four populations ofOriganum vulgare grown in North line of Iran including two subspecies (subsp.viride & subsp. vulgare) was studied for determining valuable characters for future breeding programs and medicinal purposes. In this investigation, 32 quantitative and qualitative characters were evaluated. The results showed great diversity of important characters among populations. Results of simple correlation revealed significant correlations among some important characters. Principal Component Analysis (PCA) explained about 86% of the variation related to main effective characters such as second internode length, leaf, inflorescence and peduncle length, average number of inflorescence per stem, bract, calyx and corolla color, state of calyx and bract hairs, length and width of bract and calyx and petiole length. Cluster analysis at similarity coefficient distance of about 13 divided populations in two main groups. The first main group consisted of 21 populations and the second main group included three populations. All of the specimens located in the latter group and one population from the first group belonged toOriganum vulgare subsp. vulgare, whereas the others were included in Origanum vulgaresubsp. viride.