Background. Obesity is a significant public health problem worldwide. Vitamin deficiencies, developing due to monotype nutrition, are more likely to be observed in patients than healthy children. The present study evaluates vitamin and micronutrient levels in children and adolescents with obesity and metabolic syndrome compared to healthy controls. Methods. The study included 73 patients with obesity, 64 patients with metabolic syndrome and 71 healthy children (control group) aged 10 to 16 years. Physical examinations were performed, and waist circumference and systolic blood pressure measurements were recorded. Fasting blood glucose, triglyceride, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, total cholesterol, insulin, vitamin A, vitamin E, vitamin B1, vitamin B2, vitamin B6, vitamin B12, folic acid and free carnitine levels were analyzed. The homeostatic model of assessment-insulin resistance (HOMA-IR) index was calculated and recorded. Results. The mean age of all patients was 11.9±2.6 years. The serum insulin level and HOMA-IR index were found to be significantly higher in the obesity and metabolic syndrome groups. No significant difference was found between the groups in terms of vitamin A, vitamin B6 and free carnitine levels. Significantly decreased vitamin E, vitamin B2, vitamin B12 and folic acid and increased vitamin B1 levels were observed in the obesity and metabolic syndrome groups. Conclusions. Compared to healthy children, children with obesity and metabolic syndrome may have varying degrees of micronutrient and vitamin deficiency due to poor and unbalanced eating habits. These deficiencies should also be considered in the treatment and follow-up of obesity and metabolic syndrome.