Background: Dental caries is one of the most common diseases during childhood. Saliva can modulate the process of decay, as a rich source of host factors. It has been shown that tumor necrosis factor-alpha (TNF-α) is secreted more in the saliva of individuals with active caries. No study has addressed the relationship between TNF-α levels and age or compared children's immune response at different age groups and during adolescence. Objectives: The present study aimed at evaluating the pro-inflammatory cytokine level of TNF-α in saliva and its association with caries in different age groups of children and adolescents. Methods: In this case-control study, 128 children and adolescents were divided to four age groups of 32. In each group, half of the individuals had no decay (control group) and the other half had > 4 decayed teeth (case group). Overall, 5 mL of non-stimulated saliva was spitted in sterile tubes for 15 minutes. Furthermore, 1 mL of each sample was centrifuged for five minutes at 12000 rpm. Salivary level of TNF-α was measured using the Enzyme Linked Immunosorbent Assay (ELISA) standard kit. Results: A total of 79 children were studied. The mean TNF-α levels in the case group was 35.20 ± 16.23 Pg/mL and in the control group, this was 26.20 ± 6.25 Pg/mL (P value = 0.001). The mean TNF-α level was significantly higher in the age group of six to 12 years than the age group of 13 to 18 years (P value = 0.01). Conclusions: The results of this study indicated that decay plays an important role in increasing cytokine TNF-α in non-stimulatory saliva, there is no confirming evidence of the direct effect of age on immune function yet.