Two species of commercially available natural enemies, Galendromus helveolus and Neoseiulus californicus (Acari: Phytoseiidae) were evaluated as biological control agents against Oligonychus perseae (Acari: Tetranychidae), a foliar pest of avocados in California. Densities of natural enemies and O. perseae were monitored weekly for 32 weeks on trees that were treated with either 3 consecutive releases of G. helveolus, 3 releases of N. californicus, or 3 releases of G. helveolus and N. californicus. Results were compared to trees that received 2 applications of oil and to control trees that received no treatment. Both predator species, either alone or in combination, significantly reduced numbers of O. perseae in comparison to oil-sprayed trees and control trees. Additionally, leaf damage measured as the percentage leaf area damaged by O. perseae feeding was reduced on trees treated with N. californicus alone or in combination with G. helveolus. These results demonstrated that releases of these predators should be further considered as a control treatment against O. perseae in avocados.