Potato tubermoth (PTM) Phthorimaea operculella (Lep.: Gelechiidae) is one of the pest species affecting Solanaceae worldwide. It can cause up to 80% of losses in potato open air crops as well as damage up to 100% of tubers during storage. Blattisocius (= Typhlodromus) mali (Acari: Blattisociidae), a predatory mite, was studied as a potential biological control agent of PTM. A prey acceptance bioassay of PTM eggs was carried out. Additionally, two bioassays have been conducted under microcosm conditions, which assessed the densities of mite releases at two levels of PTM infestation. The results showed that B. mali female adults accept PTM eggs as prey, and they cause a mortality rate 89.63 ± 2.47%, 48 h later. In addition to this, under microcosm conditions with potato tubers, we found at low infestation level that the effectiveness of the predatory mite varied from 72.50 ± 28.50 to 100%, 28 days later, according to the release rate of mites. Under high infestation level, the effectiveness of biological control of the pest varied from 53.36 ± 25.55 to 92.51 ± 7.88%, also according to the release rate of the mites. The possible use of biological control with B. mali of PTM, in different types of potato storage, is analysed and discussed.