Molluscs are important pests of natural and agricultural ecosystems, by feeding on different parts of leaves, stems, flowers, buds, fruits and roots of different plant hosts, reducing the marketability of annual agricultural products and damage plant species in different habitats in the country. Moreover, they are intermediate hosts of human and cattle parasites, and therefore are of medicinal and veterinary importance. In this study, snails and slugs were sampled from nine designated stations located in the south and west regions of Tehran province, considering their natural condition, vegetation, location of gardens and fields, soil or subsoil types, from the beneath of rocks and trunks, water bodies and other areas related to the habitat of snails and slugs. Samples were made using sampling nets or gathered directly by hand from plants, shrubs and river banks. Overally, 17 species belonging to 12 genera from nine families were collected and identified. Identification was done according to morphometric characters including shape, size of shell, dextral and sinistral position of the shell, operculum, aperture, radula, mucus colour, respiratory pore, keel, renal ridge and reproduction system. The highest and lowest mollusc species diversity among the stations studied were turned to be 16 and 6 species belong to station 9 (west of Tehran province) and station 2 (south of Tehran province), respectively. The most commonly diversed family was Hellicidae with 5 species, i.e., Monacha cantiana, Euomphalia pisiformis, Helicella krynickii, Helicella derbentina, Caucasotachea atrolabiata. Also, Lymnaea truncatula is identified as the most frequent species, which has medical importance. Monacha cantiana was identified in the present study and reported for the first time from Iran. All the samples and their respective spatial and temporal information were made available in the museum of the Agricultural Zoology Research Department in Iranian Research Institute of Plant Protection.