Abstract: The rotifer fauna of Iran is poorly known. This comprehensive study presents the results of an investigation of rotifers sampled in 51 freshwater sites of Tehran and neighboring provinces of Iran, from May 2006 to May 2007. Of the 115 species identified, 72 from 19 genera and 5 families are new for the fauna of Iran. Including the present records, the number of known Iranian rotifers has now reached 143. So far, the species found in Iran are overwhelmingly Palearctic. The present study is a first step towards more similar studies to update the existing species list of rotifers from all over Iran.