Delphastus catalinae Horn (Coleopetra: Coccinellidae) is one of the most important predators attacking whiteflies and was imported from Britain to control the invasive pest Bemisia tabaci in southern China. Response of the beetles to metabolite toxins from the entomopathogenic fungus, Lecanicillium (Verticillium) lecanii was studied in the laboratory and in field experiments to evaluate compatibility of the two biological control agents. Larval beetles showed slight sensitivity, while adult beetles were not susceptible to the metabolite toxins from the fungus. Consumption and foraging capacity were significantly impaired, especially for second-instar beetles which took twice as long as control beetles to consume whitefly eggs after exposure to toxins. However, no significant effect on fecundity and longevity of the beetle was observed after exposure to the toxin at field rate. The data suggest that spraying of L. lecanii or its toxins should be avoided in the field when immature stages of D. catalinae are present.