Pesticides are indispensable for safeguarding agricultural production, yet their application presents a multifaceted challenge to ecosystem integrity and sustainable pest management. This review synthesizes current knowledge on the primary ecological and agronomic consequences stemming from pesticide use, with a focus on unintended impacts. A central concern is the disruption of biological control services, as pesticides inflict lethal and sublethal effects on natural enemies, including predators and parasitoids. These effects compromise vital behaviors, physiological functions, and demographic parameters, thereby diminishing their regulatory efficacy and potentially inducing pest resurgence. Furthermore, pollinators face significant risk from systemic and contact exposure, which impairs navigation, learning, colony communication, and reproduction, threatening both biodiversity and crop pollination. Concurrently, the intensive selection pressure exerted by pesticides drives the evolution of resistant pest populations, undermining chemical control and complicating integrated pest management strategies. Compounding these issues, pesticide drift facilitates the off-target deposition of active ingredients, leading to the contamination of adjacent ecosystems and aquatic networks, which in turn affects non-target organisms and broader ecological processes. The evidence underscores that the ecological costs of pesticides extend beyond acute toxicity. Sublethal impairments to beneficial species and the evolution of resistance represent critical, long-term threats to agricultural resilience. Consequently, advancing IPM requires a concerted shift towards selective chemistries, refined application technologies, and the prioritization of non-chemical tactics to mitigate these pervasive impacts and preserve ecosystem functionality.