Purpose: Because the relationship between childhood obesity and periodontal diseases has rarely been studied, this study investigated the potential association between obesity and periodontitis among Chinese school-age children and its underlying mechanisms. Materials and Methods: The periodontal status of normal and obese Chinese children was examined and the expression of several inflammatory factors was compared between the normal and obese group. The periodontal status, including the sulcus bleeding index (SBI), plaque index (PI), bleeding on probing percentage (BOP%) and probing depth (PD) of normal and obese children was recorded. A correlation analysis between obesity degree and periodontitis was performed. The plasma levels of tumor necrosis factor-α (TNF-α) and soluble intercellular adhesion molecule-1 (sICAM-1) in gingival crevicular fluid (GCF) samples were examined using ELISA. Results: No obvious correlation was observed between obesity and the four clinical periodontal indices SBI, PI, SBI and BOP% was observed, which is in contrast to the contribution of obesity to periodontitis in adults. However, the concentration of serum TNF-α was significantly elevated in the obese group (219.91 ± 24.57 pg/ml, n = 30) when compared with the normal group (169.31 ± 23.62 pg/ml, n = 23) (t = 2.844, p 0.05), indicating that obesity still reinforces the inflammation responses in the periodontium. Conclusion: Among the Chinese school-age children, obesity leads to the accumulation of TNF-α in the gingival crevicular fluid, which occurs much earlier than and may contribute to the development of periodontitis associated with obesity. Palabras clave: children, obesity, periodontitis, TNF-α