<p><strong>Background:</strong> The prevalence of obesity in Chilean preschoolers is high. Simple methods for the diagnosis in Chilean preschoolers are of public health interest. We determined neck circumference cut-off points as a proxy measure of obesity according to age and sex.</p><p><strong>Methods:</strong> 597 participants (267 girls) were included. NC, weight, height, and waist circumference were measured. Body mass index scores (BMI z scores) was calculated. Descriptive variables for girls and boys were compared with t-test. Pearson correlations were calculated to examine the relationship of NC with classical anthropometric measures.<strong> </strong>NC cut-off values (ROC analysis) and Kappa coefficient, were calculated.</p><p><strong>Results:</strong> NC was positively associated with BMI z score and WC among girls and boys, across age groups (all p&lt;0.001). Obese cut-off points of NC for elevated BMI z score were between 25.3~25.9 cm in girls and 26.2 in boys, while those for WC were, 25.7 and 26.3 for 5-year-old girls and boys, respectively. The KC between BMI z score or WC with NC had an agreement strength between poor to moderate (all p&lt;0.001).</p><p><strong>Conclusions:</strong> NC demonstrated to be a reliable indicator for the diagnosis of obesity for Chilean preschoolers. Future studies are needed to validate this finding.</p>