Prior to this research, no data were available on arboreal mites in the Arsi Mountains National Park, central Ethiopia. A list of six species representing six genera and five families associated with Acacia spp. is presented. of these, the taxa Eremellidae, Afreremella, A. luisiae, and Scapheremaeus cf. cornutus are reported for the first time for the fauna of Ethiopia. two new species—Phauloppia arsizonensis sp. nov. (oribatulidae) and Unguizetes (Unguizetes) acacicus sp. nov. (Mochlozetidae)—are described, based on adult females. Phauloppia arsizonensis sp. nov. is characterized mainly by a narrowly rounded rostrum, short and globose bothridial seta, thickened and heavily barbed lamellar, interlamellar, and notogastral setae, an elongate oval porose area Aa, and a short circumpedal carina. Unguizetes (Unguizetes) acacicus sp. nov. is characterized mainly by a foveolate notogaster and anogenital region, and acicular notogastral setae. Podoribates rectus is transferred to Unguizetes (Unguizetes). Identification keys to the Afrotropical species of Phauloppia and to the known species of Unguizetes are provided.