Many species of Mesostigmata soil mites have potential as biological control agents of pests and parasites. Although still poorly studied, some species of the family Ascidae have shown promise for controlling harmful organisms, particularly nematodes. These mites are considerably smaller than commercially used species from the families Laelapidae and Macrochelidae. This study evaluated the predation potential of Gamasellodes lavafesii (Ascidae) on the root-knot nematode Meloidogyne javanica (Heteroderidae), an important plant parasite, and the gastrointestinal nematode Haemonchus contortus (Trichostrongylidae), a major parasite of sheep. Additionally, potential alternative food sources for future mass rearing were assessed by offering ad libitum eggs of Ephestia kuehniella (Lepidoptera: Pyralidae) and different developmental stages of Glycyphagus destructor (Astigmata: Glycyphagidae), Thyreophagus cracentiseta and Tyrophagus putrescentiae (Astigmata: Acaridae), and Rhabditella axei(Nematoda: Rhabditidae). For the nematodes test, each experimental unit consisted of an acrylic Petri dish (2 cm high × 3 cm diameter), lined with a 0.5 cm agar layer and provided with an inert substrate for oviposition. For the other prey, each experimental unit consisted of the same acrylic Petri dish, with a base of plaster of Paris and activated charcoal (9:1), kept moist by daily water addition. A gravid female of G. lavafesii was introduced per unit. Treatments consisted of daily provision of: (1) 500 J2 of M. javanica or (2) 500 J3 of H. contortus. The other prey were supplied ad libitum. Predation and oviposition were recorded daily for ten days, with 30 replicates per treatment. Higher predation and oviposition rates were observed when the predator fed on M. javanica (245.7 prey/day and 3.0 eggs/day, respectively) compared to H. contortus (204.1 and 1.6). Among alternative food sources, the highest oviposition rates were observed with R. axei (8.0 eggs/female/day) and T. cracentiseta (3.4 eggs/ female/day). These results indicate strong acceptance of both plant- and animal-parasitic nematodes, as well as promising potential for large-scale mass rearing. This study represents an initial step toward the applied use of this predator in biological control programs. Funding: FAPESP (2019/27793-7) - BIOTA FAPESP (2017/12004-1) - Koppert do Brazil Holding S.A.