Cuscutaceae family is reviewed based on the literature and available herbarium materials. This is a monotypic family and includes a single genus, three subgenera and eighteen species in Iran, among them Cuscuta haussknechtii Engelm, is the only endemic species in Iran. This genus has been studied for the ongoing project of the Flora of Iran. The study was based on fresh materials from field as well as herbarium specimens. All specimens existed in the herbaria of Research Institute of Forests and Rangelands (TARI), herbarium of Iranian Research Institute of Plant Protection (IRAN), Ferdowsi University of Mashad (FUMH), Research Center of Agricultural and Natural Resources of Fars Province were revised. A synopsis and identification key is provided to the eighteen species. Diversity centers and distribution of taxa in Iran are presented. Also the checklist of accepted species, synonyms, typical characters of the taxa are given. In this research new localities and new host plants are added to species and a new variety C. lehmanniana var. lehmanniana is introduced as a new record to Iran.