Objective: To analyze the characteristics of latent classes of dietary patterns among children and adolescents in Qinghai Province, and their association with overweight and obesity, so as to provide a scientific basis for conducting targeted nutritional interventions and weight management for the local population. Methods: From May to October 2025, a multi stage stratified cluster random sampling method was employed to recruit 1 611 children and adolescents aged 6-17 years from Chengdong District of Xining City and Gonghe County of Hainan Tibetan Autonomous Prefecture in Qinghai Province. Questionnaire survey was conducted using a questionnaire developed by the Chinese Center for Disease Control and Prevention, and physical examination was conducted by using unified measurement standards. Latent class analysis (LCA) was performed on the food intake frequency of the participants. The χ 2 test and Logistic regression analysis were applied to explore the relationship between dietary patterns and overweight/obesity. Results: The detection rates of overweight, obesity, and overall overweight/obesity among the participants were 10.4%, 5.8%, and 16.2%, respectively. Latent class analysis identified three dietary patterns: modern mixed pattern ( n =399, 24.8%), low diversity pattern ( n =476, 29.5%), and traditional dietary pattern ( n =736, 45.7%). The potential category distribution differences of three dietary patterns among children and adolescents with and without overweight or obesity were statistically significant (non overweight and obesity: 22.5%, 29.1%, 48.4%; overweight and obesity: 36.4%, 31.8%, 31.8%) ( χ 2=30.69, P <0.01). Logistic regression showed that, compared with the traditional dietary pattern, the modern mixed pattern was associated with a higher risk of overweight and obesity ( OR =1.68, 95% CI =1.13-2.49); female sex was associated with a lower risk of overweight/obesity compared with male sex ( OR =0.66, 95% CI =0.50-0.86) (both P <0.05). Conclusions A positive association exists between the modern mixed dietary pattern and obesity in children and adolescents. It is recommended to reduce the intake of grains and unhealthy foods among overweight and obese children and adolescents, while increasing the consumption of legumes, fish, and shrimp, in order to cultivate healthy and rational dietary habits.