Introduction. Neck circumference is a useful anthropometric measure for identifying adiposity in children; however, few percentiles are available for school-aged children in northwestern Mexico. Objectives. To estimate smoothed percentiles of neck circumference by age and sex, and to evaluate their association with anthropometric and adiposity indicators in schoolchildren aged 7 to 12 years in northwestern Mexico. Population and methods. We conducted a cross-sectional study among 319 schoolchildren aged 7 to 12 years from four elementary schools in Ciudad Obregón, Sonora. Weight, height, neck circumference, waist circumference, triceps skinfold thickness, and body fat percentage (measured by electrical bioimpedance) were measured. We estimated smoothed percentiles using the LMS method. Results. We included 174 girls and 145 boys. Smoothed percentiles (P10, P25, P50, P75, and P90) were estimated by age and sex. Neck circumference was positively correlated with age-adjusted body mass index (BMI), waist circumference, body fat percentage, and triceps skinfold thickness. Conclusion. Neck circumference showed a positive association with anthropometric and adiposity indicators, suggesting that it could serve as a complementary anthropometric measure for assessing adiposity in this population.