Background <p>Childhood overweight/obesity is prevalent in the United States and is a prominent health concern. In this study, we aimed to investigate relationships between child body mass index (BMI) percentile and brain cortical structure that may impact executive functions in late childhood.</p> Methods <p>Seventy-seven children (43 with normal weight, 23 girls and 20 boys; 34 with overweight/obesity, 16 girls and 18 boys) were included and underwent a brain MRI as well as an assessment of executive functions by Delis-Kaplan Executive Function System (D-KEFS). Brain cortical features including thickness, surface area, volume, and local gyrification index were extracted from the MRI. Multivariable linear regression models were used to evaluate the associations between child BMI percentile and regional cortical features, and between cortical features and executive functions, with appropriate multiple comparison corrections. We also controlled for several maternal and family socioeconomic parameters which are potential confounders.</p> Results <p>Significant negative associations were identified between BMI percentile and cortical thickness in the left inferior temporal gyrus (ITG-L) (ꞵ= -0.0022 FDR-corrected <i>P</i> = 0.04), left rostral middle frontal gyrus (RMFG-L) (ꞵ= -0.0016, FDR-corrected <i>P</i> = 0.03), and right fusiform gyrus (FFG-R) (ꞵ= -0.0019, FDR-corrected <i>P</i> = 0.04). Furthermore, positive associations between cortical thickness and motor speed subscale in D-KEFS were identified in the ITG-L (ꞵ=5.23, <i>P</i> = 0.006) and MFG-L (ꞵ=8.22, <i>P</i> = 0.005).</p> Conclusions <p>Associations between BMI percentile, brain cortical structure in frontal and temporal lobes, and executive functions were found in children aged 10–12 years. Our results indicate that body weight status during childhood may potentially impact brain cortical development that is associated with executive functions in school age children.</p>