During a three-year survey of oribatid mites in soil and leaf litter of Andean North patagonian forests, specimens belonging to the genus Oxyoppia were collected. Even though the specimens could be recognized by the use of previous descriptions and existing keys as being close to Oxyoppia (Oxyoppiella) suramericana, morphological analyses suggest enough differences to propose a new species Oxyoppia mustaciata n. sp. A new identification key to species of Oxyoppiinae from Argentina is provided.