Objective: To explore the current situation of Internet addiction among junior high school students in Inner Mongolia and its associated factors, so as to provide a theoretical basis for the prevention and control of Internet addiction among junior high school students. Methods: In September 2023, 53 755 junior high school students were selected by stratified cluster random sampling method from all the flag counties in Inner Mongolia, and questionnaires were administered according to the "Monitoring and Intervention Program of Common Diseases and Health Influencing Factors of Students, by using the Internet Addiction Inventory and Generalized Anxiety Disorder Scale-7 Item. The Chi test and multiple Logistic regression analysis were used to explore related factors and draw nomograms. Results: The reported rate of Internet addiction among junior high school students in Inner Mongolia was 2.15%. The results of multivariate Logistic regression analyses showed that students were more likely to be in higher grades (grade eight: OR =1.54; grade nine: OR =1.64), being scolded by their parents ( OR =1.06), living in the school ( OR =2.28), being bullied in the school ( OR =1.91), anxiety symptoms ( OR =3.15), and substance abuse (smoking: OR =2.56; drinking alcohol: OR =2.29; inhaling soluble solvents for pleasure: OR =2.17; using cough suppressant except for coughing: OR =1.50; using sedatives without doctor s permission: OR =1.34) were positively correlated with Internet addiction among junior high school students in Inner Mongolia ( P <0.05). The area under the curve was 0.819, and the calibration curve showed that the predicted values were basically consistent with the measured values. Conclusions Internet addiction among junior high school students in Inner Mongolia is related to students living environment and substance abuse behavior. Attention should be paid to the living environment of junior high school students and strengthen the preventive education of substance abuse in order to reduce the occurrence of Internet addiction among junior high school students.