High weight and obesity represent risk factors for numerous diseases. Correlations between body mass index (BMI) and carious lesions have also been described. In the present study, a possible association between caries prevalence and high weight ranges were examined in 2071 primary school pupils (51.8 % girls, 48.2 % boys), aged 6 to 10 years. A dental examination including the assessment of carious lesions (df-t + DF-T) was followed by measurements of height and weight in order to determine the BMI. The evaluation showed that 6.8 % of the elementary school children were underweight, 76.4 % had a normal weight, and 10.5 % were overweight and 6.3 % obese. Underweight children showed healthy teeth in 50 % of the cases, 47.4 % with normal weight showed naturally healthy teeth, while overweight and obese children displayed naturally healthy teeth in 41.5 % and 38.3 % of the cases, respectively. In primary school pupils, a significant association between the caries frequency and the BMI was found. A low BMI showed a correlation with the absence of carious lesions (p < 0.0001), and a high BMI was linked to a high number of caries lesions (df-t + DF-T values; p = 0.0021). However, no gender-related differences, regarding the prevalence rates for high weight and obesity, could be established. The significant correlation between the BMI and caries frequency persisted even after adjustment to the age of the children.