Body mass index (BMI) reference curves are used to assess children's health. The aim of this work is to construct BMI reference curves for Tunisian children and adolescents and compare them with local and international references. The BMI reference curves were constructed using the LMS method using data from 4358 Tunisian children (2182 girls and 2176 boys) aged 0–18 years. The result of this study presents the smoothed percentile curves of BMI on the basis of age and sex of Tunisian children. The reference curves of Tunisian children demonstrated some variations in comparison with the median percentiles with the references of the International Obesity Task Force (IOTF), the World Health Organization (WHO), and with local references from Algeria and Turkey. The prevalence study indicated that the rate of overweight has increased mainly in adolescent children. Conclusion: the new BMI reference curves could help pediatricians and fitness specialists to assess the nutritional status of Tunisian children and to reduce disease and obesity risks.