The predatory efficacy of phytoseiid mites, Neoseiulus barkeri was evaluated against onion thrips in controlled conditions. Different larval instars and adult thrips were provided as prey in different combinations (choice) or separately (no-choice). In choice test, no significant difference was observed in total thrips consumption per day. But in both observation hours (12 h or 24 h), a significant difference was observed between the feeding of immature and adult thrips. In a no-choice test,when we confined N. barkeri to feed on a specified diet of T. tabaci (first instar, second instar, or adults separately), a significant difference in total thrips consumption per day was observed in each prey group. In both tests, predatory mites fed more on first larval instar thrips compared to second larval instar and adults. However, consumption rate was rather higher during initial feeding hours (12 h) and slowed down later (24 h); this may be due to aggressive predation initially. The findings suggest that N. barkeri feed more on younger instars of T. tabaci and if these predators are released during early pest outbreak it will control the thrips population.