Abstract BACKGROUND The rising demand for environmentally friendly pest control highlights the importance of understanding the interaction between natural enemies and pesticides. Amblyseius swirskii , a predatory mite extensively used in biocontrol, plays a crucial role in managing pest populations in agricultural systems. Integrating this mite with selective pesticide use within integrated pest management (IPM) would significantly advance pest control and may reduce pesticide residues in the environment and agricultural produce. This study characterized the susceptibility of two Amblyseius swirskii colonies to deltamethrin, a widely used pesticide, to assess their potential integration into IPM strategies. RESULTS Both colonies exhibited significant tolerance to deltamethrin at concentrations higher than the maximum recommended field rate. Our analysis identified mutations in the target site in both populations. The commercial population also showed a contribution of cytochromes P450 to the resistant phenotype. Despite these results, semi‐field trials revealed a significant reduction in mite counts post‐treatment with deltamethrin; various experiments were conducted to understand this discrepancy. CONCLUSION This study underscores the need for comprehensive evaluations of pesticide impacts on biological control agents to optimize IPM strategies. Understanding pesticide resistance and field performance dynamics is crucial for developing sustainable pest management practices that ensure environmental resilience and agricultural productivity. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.