Culex pipiens (L.) (Diptera: Culicidae) is regarded as a significant pathogen vector. Using the standard procedures advised by the WHO organizations, the toxicity of three insecticides (two biocides and chlorpyri-fos-ethyl) was assessed in this study against field and laboratory of third-instar C. pipiens larvae at varying concentrations after 24, 48, and 72 hours.Additionally, three insecticides were identified using a biochemical assay, total protein, invertase, protease, glutathione-S-transferase (GST), α, β esterases (ESts), and acetylcholin-esterase (AChE) activity for both field and lab strains. The findings demonstrated that the field strains taken from Arab El-Raml, Al Menofia Governorate, were less susceptible to the tested pesticides than the laboratory strain, and that the percentage of death increased gradually as the insecticide concentration increased. When comparing the field strain to the laboratory strain, the biochemical impacts revealed that all pesticides raised the activity levels of both acetyl cholinesterase (AChE), glutathione S-transferase (GST), and α, β esterases (ESts), indicating that the field strain had the highest resistance. On the other hand, following pesticide treatment, total protein, invertase, and protease levels dropped. Detoxifying enzyme activity often increased gradually as generation numbers grew, suggesting that elevated resistance is probably linked to elevated activity of target and metabolic enzyme systems.