Culicid mosquitoes pose significant threats to both animal and human health due to their ability to transmit various parasitic and viral diseases. In light of the problems arising from the overuse of synthetic insecticides, there is an urgent need to explore alternative solutions. Nanotechnology offers promising advancements, enhancing the efficacy of products across various fields, including the food industry, pharmacy, and agriculture. One notable application is the development of nanoinsecticides, which exhibit superior penetration capabilities into target insect pests due to the small size of nanoparticles and their high efficiency resulting from a larger surface area. This research evaluated the effects of a nanoemulsion of Pimpinella anisum essential oil on the third instar larval stage of Culex pipiens. The lethal concentration (LC50) used for treatment was 40ppm. The studied nanoinsecticide induced significant histopathological and biochemical alterations in the larvae post-treatment. Biochemical assessments revealed a notable decrease in alkaline phosphatase enzyme activity in the treated larvae. Histopathological changes were analyzed using transmission electron microscopy, which showed significant alterations in muscle and midgut tissues after 24 hours of exposure to the nanoemulsion. Observed changes included cytoplasmic vacuolization, elongation of epithelial cells, damage and disorganization of microvilli, and degeneration of the muscle layer.