The family Laelapidae includes ca. 90 known genera and over 1300 known species in nine subfamilies, and mites of this family are soil-dwelling predators, arthropod symbionts and obligate and facultative ectoparasites of mammals (Evans and Till 1966; Casanueva 1993; Lindquist et al. 2009; Beaulieu et al. 2011). Bregetova (1956) erected the subfamily Myonyssinae which includes laelapid mites usually associated with small mammals. So far more than 100 species of laelapid mites have been reported from Iran, but only a few of them were collected in association with small mammals and none of them belongs to Myonyssinae (Kazemi and Rajaei 2013). During an investigation on Mesostigmata in Arasbaran Forests, East Azerbaijan Province, Iran, mite specimens were extracted from soil and litter using BerleseTullgren funnels, cleared in Nesbitt's fluid and mounted on microscope slides in Hoyer's medium. In this research, a female specimen of Myonyssus gigas (Oudemans, 1912) was collected in soil and litter near a hole, possibly belonging to an unknown small mammal, the typical hosts of myonyssine mites. This record is the first report of the subfamily from Iran. Diagnosis for the genus and species followed Evans and Till (1966) and Masan and Fenda (2010).