Background: The article explores the development of aggression in children in kindergartens in Sari City, examining the influence of psychological, social, biological, and environmental factors, including intestinal parasite infection, which can lead to neuropathic disorders, behavior, anemia, and malnutrition. Methods: Between 2015 and 2016, a cross-sectional study was conducted on 100 kindergarten children in Sari City, with 47 suffering from intestinal parasites and 53 suffering from the disease. Data was collected using grade tests and questionnaire sheets, using cluster sampling. Results: The study revealed that 24% of 24 children in kindergartens were aggressive, with 12 infected and 12 uninfected. There was no significant difference between children infected or uninfected, and no significant relationship was found between aggression rates in boys and girls. Conclusion: Our results demonstrate that, despite the significant relationship between aggression and intestinal parasite infection, the risk of exposure to aggression is higher in infected children, and the results represent that many factors should be studied about children’s aggression simultaneously.