Aim: This study aimed to evaluate the relationship between vitamin D levels and insulin resistance parameters in children with overweight and obesity. Material and Methods: A total of 174 children, 64.4% (n=112) female, and 35.6% (n=62) male, aged between 6-17 years were included in the study. The participants were divided into three groups as normal (29.9%, n=52), overweight (23.6%, n=41), and obesity (46.5%, n=81) based on the criteria of the World Health Organization body mass index (BMI) classification. The insulin resistance status of the participants was evaluated by homeostatic model assessment of insulin resistance (HOMA-IR), fasting glucose to insulin ratio (FGIR), and quantitative insulin sensitivity check index (QUICKI). Results: HOMA-IR was found higher in the obesity group (3.2±2.1) compared to the overweight (2.2±1.0) and the normal weight (1.5±1.0) groups (p<0.001). It was observed that QUICKI values of the overweight (0.34±0.03) and the obesity (0.33±0.03) groups were lower than the normal weight (0.37±0.03) group (p<0.001). FGIR was noticed as higher in the normal weight (16.8±10.4) group compared to the overweight (10.6±6.0) and the obesity (8.5±5.5) groups (p<0.001). The mean serum 25-hydroxyvitamin D [25(OH)D] levels of the children and adolescents were 19.6±10.7 ng/mL, and no statistically significant difference was found between the groups (p=0.153). A significant weak negative correlation between serum 25(OH)D and HOMA-IR values was found (r=-0.170, p=0.025). Additionally, a weak positive statistically significant correlation was found between serum 25(OH)D level and QUICKI and FGIR values (r=0.173, p=0.022, and r=0.173, p=0.023, respectively). Conclusion: Vitamin D levels can affect insulin resistance parameters.