The Tenuipalpidae are small, slow-moving, flat, red or green phytophagous mites that, despite the economic importance of some species, has been studied much less than the Tetranychidae. They have a great number of host plants including cultivated plants, ornamentals, fruit crops and forest trees. The aim of this study was to determine the species composition of tenuipalpid mites in the northern part of Iran, Mazandaran province. More than 150 plant species belonging to 41 families were inspected for possible infestation with tenuipalpid mites, among which 28 plant species were infested. Most of the infested plants are new records for the respective mite species. A total of 14 species of tenuipalpid mites belonging to five genera were collected and identified. Though citrus is the major fruit crop grown in Mazandaran province, flat spider mites were not yet reported from it in this area. In addition to this faunistic study, a male of Cenopalpus rubusi, which was collected on Rubus persicus Boiss, is described for the first time