In the field of ethnopharmacology, precise identification of collected medicinal plants plays an important role to take a plant-derived compound from local traditional healers to the pharmacy. Therefore, this study is concerned with botanical research on medicinal plants of Semnan province (Iran). According to 379 collected herbarium specimens, 244 medicinal species belonging to 66 plant families and 102 genera were identified. The largest families were Lamiaceae (29 species), Asteraceae (27 species), and Fabaceae (19 species). The most frequently used plant organs were leaves and aerial parts. The most treated used category was the digestive system, followed by the metabolic and immune system, urological problems, respiratory system, gynecology, and dermatological problems. The outstanding therapeutic effects of some less widely known species which traditionally are used among indigenous people were reviewed. The fundamental role of botanists in pharmacological research and the disadvantages of wrong identifications in this field were highlighted