The two-spotted spider mite, Tetranychus urticae Koch, is one of the most important phytophagous pests and since wide host plants range, high reproductive potential and high potential to develop resistance to chemical pesticides, cause severe damage to agricultural products worldwide. High reliance on chemical pesticides to decrease population density of this pest has resulted undesirable effects in different agro-ecosystems and therefore, utilization of natural enemies could be considered as a promising strategy for reducing such negative effects. In the present study, LC50 effects (1.3 * 106 con/ml) of entomopathogenic fungus Beauveria bassiana (Bals.) Vuill. (strain MZ) on choice and no-choice feeding preference and switching behavior of predatory mite Phytoseiulus persimilis Athias-Henriot feeding on different life stages of the two-spotted spider mite (egg, larvae, protonymph, deutonymph, adult male and adult female) were evaluated under laboratory conditions at 25 ± 1 ºC, relative humidity of 65 ± 5 % and a light period of 16 h. Switching behavior of the predatory mite was studied on the different ratios (10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30: 80:20 and 90:10 egg: adult female) of egg and adult female of the two-spotted spider mite. According to results obtained, in no-choice preference (without B. bassiana), the highest preference of predatory mite P. persimilis was observed to egg stage (15.22 ± 0.57 egg). The lowest feeding was recorded on the adult female of two spotted spider mite (2.33 ± 0.50 adult female). In this test (with B. bassiana), the highest and lowest feeding rate was recorded on the larvae and adult male of T. urticae (4.90 ± 0.64 larvae and 1.30 ± 0.40 adult male, respectively). In choice preference (without entomopathogenic fungus), the highest feeding rate was observed on egg stage (14.75 ± 0.56 egg). Furthermore, predatory mite P. persimilis has the lowest preference to adult male (0.25 ± 0.16 adult male). In this test (with B. bassiana) the highest and lowest feeding rate was recorded on larvae (9.90 ± 0.53 larvae) and adult female (0.20 ± 0.13 adult female), respectively. In switching assay (without entomopathogenic fungus), P. persimilis was changed its feeding preference from egg to adult female in low density of egg stage. When the egg was treated with B. bassiana, the switching behavior was observed with higher severity. Our findings confirmed significant effects of B. bassiana on preference and switching behaviors of P. persimilis and therefore, during simultaneous application of these natural enemies, more attention should be devoted to evaluate their possible interactions.