The ornamentally important genus Adonis L. (Ranunculaceae) consists of about 30 species. In Iran, 8 species are recognized. The new classification system recognizes two subgenera, six sections, and six series for Adonis. The species differentiation within the genus is controversial due to morphological overlaps in different species and extensive morphological variation. Therefore, the aims of present study were: 1- Species delimitation within the Sect. Adonis based on morphological and molecular evidences and, 2- Studying the species relationship based on molecular phylogeny. Multivariate analyses of morphological and molecular (ITS and ISSR) data differentiated the Adonis species. PCA biplot analysis of morphological characters revealed morphological characters such as leaf arrangement; leaf length, flower diameter, petal length and width, calyx length, and pedicel length are of taxonomic implication in Adonis. Bayesian tree of ITS sequences revealed that the sect. Adonis is differentiated from the sect. Adonanthe. Based on ITS data, A. microcarpa showed close affinity to A. scrobiculata, while A. aestivalis, A. icrocarpa and A.dentata were close to each other.