The aim of this study was to investigate the therapeutic effects of propolis for the toxicity of cypermethrin (CYP) on histopathological changes in tissues of rainbow trout (Oncorhynchus mykiss). CYP is one of the most toxic pyrethroids highly for the aquatic organisms. The fish were exposed to three sublethal concentrations of CYP (0.0041, 0.0082 and 0.0123 ppm). In addition, different concentrations of propolis (10, 20 and 30 ppm) were used in the investigation for the period of 96 h. Propolis was collected by honeybees from different plants to prevent oxidative damages as an antioxidant. The therapeutic concentration of propolis was determined at 10 ppm. 10 ppm propolis was added to three cypermethrin concentrations. Shorting the secondary lamellae, fusion of secondary lamellae, oedema, necrosis, vacuolization and cartilage damage in gill tissue of fish exposed to CYP were observed by histopatological analyses. Hepatic lesions in liver tissue of fish exposed to CYP were characterized as hydropic degeneration, necrosis, mononuclear cell infiltration and narrowing of sinusoids. The most common changes in muscle tissues at all concentrations of CYP were nuclear proliferation and congestion. Besides, 10 ppm propolis on gill, liver, muscle tissues of rainbow trouts showed significant therapeutic effects. Histological analysis revealed that propolis may serve as an antitoxic agent against pesticide toxicity.