Dental caries is the most common, chronic, noncommunicable, preventable oral disease worldwide. Oxidation may play an important role in dental caries initiation and progression. Antioxidants in body fluids protect cells. The aim of this study was to evaluate salivary and serum total antioxidant capacity (TAC) and malondialdehyde (MDA) levels in dental caries. A total of 118 healthy caries-free and caries-active male and female students participated. Caries was detected clinically. Unstimulated whole-saliva samples and blood samples were obtained. Sialochemical analysis was carried out by spectrophotometric assay. Data were analyzed with the Student t test using STATA 11. Salivary and serum TAC levels in the case and control groups did not show any significant differences. Mean salivary MDA levels in the case and control groups were 0.71 ± 0.1 and 0.35 ± 0.06 nmol/mL, respectively. The results showed significantly higher levels of salivary and serum MDA in the case group compared to the healthy control group. The oxidative stress marker was significantly higher in the caries group compared to the healthy control group. Antioxidants were not significantly different between the two groups. MDA can be produced by dental caries, resulting in a decrease in antioxidant levels, causing disease progression. Further studies are necessary to determine whether MDA is the cause or effect of the disease.