Introduction <p>Obesity is a major health threat of modern civilization with substantially increased prevalence which affects children’s health, growth, and development. Also, tooth eruption is certainly linked to the somatic development of the person.</p> Aim <p>This study aimed to assess the association between the eruption of permanent teeth and obesity among a sample of primary school children from Tanta City.</p> Methods <p>A case-control study was carried out on 2520 healthy students aged 6–12 years selected from 10 primary schools in Tanta City (equally included from public and private schools). The selected students were divided into equal sub-groups according to age, gender, and obesity status using a stratified random sampling technique. Obesity was assessed using BMI method while tooth eruption was recorded when any part of the crown was visible through the oral mucosa for twenty-eight permanent teeth. Statistical analysis was done for the collected data.</p> Results <p>All permanent teeth in the maxillary and mandibular arches erupted earlier in private school children, except for the lower right second molar showed earlier eruption in public school children with no significant difference. The mean eruption age of all permanent teeth differed significantly between public and private institutions except for upper and lower right and left second molars, lower right first premolar, and lower right and left central incisors.</p> Conclusion <p>This population-specific research revealed a highly significant positive association between the total number of permanent teeth erupted and BMI among school children aged 6–12 years from Tanta City.</p>