Introduction: Selenium is an essential trace element involved in different physiological functions of the human body. An inverse relationship between serum selenium levels and cervical intraepithelial neoplasia has been reported. cervical intraepithelial neoplasia is regarded as a potentially premalignant transformation of squamous cells of the cervix. Objectives: To evaluate the relationship between the serum level of selenium and cervical intraepithelial neoplasia. Methods: A case-control study was conducted at Baghdad Teaching Hospital and Iraqi National Cancer Research Center in the University of Baghdad during the period from July 2021 to July 2022. A convenient sample of 100 women was enrolled in the current study and included case group which consisted of 50 women who were diagnosed with cervical intraepithelial neoplasia and control group which consisted of 50 women who did not have cervical intraepithelial neoplasia as confirmed through histological examination after punch biopsy by colposcopy. Results: The serum level of the selenium was significantly lower in the case groups compared to the control groups (P-value=0.001). In addition, the proportion of the participant with abnormal levels of selenium was significantly higher in the case group compared to the control group (P-value=0.001). In the case group, there was a significant difference between the cervical intraepithelial neoplasia grade regarding the serum level of selenium, the level of selenium significantly decreased with the progression of the disease (P-value=0.001). Conclusions: Selenium deficiency may significantly increase the incidence of cervical intraepithelial neoplasia. In addition, it significantly impacts the transformation to a higher degree as there was a significant difference between cervical intraepithelial neoplasia I, II, and III regarding the level of serum selenium.