Background <p>Childhood overweight/obesity stems from complex interactions among genetic, environmental, and behavioral factors, with diet being a key modifiable determinant. However, evidence on the association between dietary patterns and overweight/obesity remains inconclusive.</p> Methods <p>We conducted a cross-sectional study to investigate the association between dietary patterns and overweight/obesity among 13,312 school-aged children (6–12 years) in Hainan Province, China, from January 2021 to June 2022. We recorded the height and weight of each child and calculated their body mass index (BMI). The z-score for BMI for age was calculated using the WHO-recommended AnthroPlus software, and diagnoses of overweight and obesity were determined according to the WHO criteria. Dietary information on school-age children was collected by a validated food frequency questionnaire, which covered the most common foods consumed in Hainan, China. Factor analysis was conducted using principal component analysis and varimax rotation to group food items with factor loadings &gt;0.5. Subsequently, K-means clustering was applied to classify children into five dietary pattern clusters. Logistic regression was used to explore the relationship between dietary patterns and overweight/obesity in school-aged children.</p> Results <p>The study identified five distinct dietary patterns among school-aged children in Hainan Province. Traditional (<i>n</i> = 2,039, 15.32%): Dominated by staple foods, meat, eggs, and fruits. High-fat and high-protein (<i>n</i> = 3,469, 26.06%): Characterized by high consumption of nuts, beans, aquatic products, and dairy products. Balanced (<i>n</i> = 5,560, 41.77%): Marked by a balanced intake of staple foods, meat, eggs, fruits, vegetables, nuts, beans, aquatic products, and dairy products. Dried fruits (<i>n</i> = 676, 5.08%): Primarily consisting of dried fruits. Snacks (<i>n</i> = 1,568, 11.77%): Mainly composed of sugary drinks, puffed foods, fried foods, and dried fruits. Balanced dietary pattern is the main dietary pattern for school-age children in Hainan Province. Compared to the balanced dietary pattern, the traditional pattern (OR = 0.88, 95%CI : 0.75–1.03) and dried fruit dietary pattern (OR = 1.13, 95%CI : 0.91–1.40) showed no significant association with overweight/obesity after multivariable adjustment. To avoid clinically trivial effects in this large sample, we applied a conservative effect size threshold (OR ≥ 1.2). Only the snack-based dietary pattern showed a clinically meaningful association with overweight/obesity after multivariable adjustment (OR = 1.22, 95%CI : 1.04–1.43). The high-fat, high-protein pattern showed a statistically significant but clinically negligible association (OR = 1.15, 95%CI : 1.03–1.30), which did not meet the predefined clinical relevance criterion.</p> Conclusion <p>School - aged children with snack - type dietary pattern had a higher likelihood of overweight/obesity than those with balanced dietary patterns.</p>