The efficacy of the fungus Lecanicillium lecanii and two bacteria, Bacillus thuringiensis and Streptomyces avermitilis against the two-spotted spider mite Tetranychus urticae Koch and side effects on its predatory mite Phytoseiulus persimilis A.-H. was studied under laboratory conditions. Both S. avermitilis and B. thuringiensis based biopesticides resulted in maximum mortality rates of 90–100% and 91–99% for spider mite adults and larvae, respectively. The mortality of spider mite larvae under fungus L. lecanii treatment was around 60%. These bacteria and fungus also had toxic effects against P. persimilis on the same day of applying insecticides and releasing the predatory mite. The release of predatory mites one day post-treatment of plants with L. lecanii and 7 days post-treatment with B. thuringiensis or S. avermitilis did not negatively affect the survival of predators released. These findings support the potential use of entomopathogenic fungi and bacteria in combination with predatory mites in spider mite biocontrol.