Abstract: Cosmolaelpas qassimensis sp. nov. was collected from soil samples containing leaf litter and soil surrounding the root system of date palm trees during 2013-2014 in Qassim, Saudi Arabia. Monthly survey showed that C. qassimensis was at its highest rate of occurrence (13.96 individuals/ sample) in September. There were no significant differences between average number of mites collected in May, July, August and October, while it was rarely found (1.25 and 0.96 mites/ sample) in January and February, respectively. Immature stages and adult female and male of C. qassimensis sp. nov. were extracted from a pure laboratory culture, which were maintained feeding on the acarid mite, Tyrophagous putrescentiae Schrank and kept at 26±1°C and 70±5% RH. They were illustrated and identified.