Cypermethrin is a potential toxic pollutant that directly threatens the aquatic ecosystems and environment. Propolis, a natural product collected from plants by honey bees has many functions, such as antimicrobial, antioxidant, and anti-inflammatory. This study attempted to detrmine some biochemical and microbiological parameters of rainbow trout fillets after exposure to propolis and cypermethrin. The results of the current study revealed that levels of malondialdehyde (MDA), lactic acid, total volatile base-nitrogen (TVB-N), total counts of psychrophilic, and mesophilic bacteria increased in cypermethrin groups (P<0.05), compared to control group. Furthermore, there were no significant differences in pH levels between groups. Additionally, levels of MDA, lactic acid, TVB-N, count of psychrophilic, and mesophilic bacteria in cypermethrin+propolis treated groups were significantly reduce in comparison to exposed groups with cypermethrin (P<0.05). The findings also showed that the fillet quality some biochemical and microbiologic functions of fishes could be changed in groups that exposed to cypermethrin by propolis.