Background: Dietary total antioxidant capacity serves as an indicator for dietary quality and reflects daily antioxidant intake. This study aimed to determine the oxidative stress status of patients with schizophrenia and to examine the relationship between dietary total antioxidant capacity (dTAC) and 8-hydroxy-2′-deoxyguanosine (8-OHdG), a marker for oxidative stress. Methods: This study was conducted in Turkey and involved 40 patients diagnosed with schizophrenia or schizoaffective disorder according to the Diagnostic and Statistical Manual of Mental Disorders, 5th ed and 30 healthy controls matched for age and gender. The participants’ sociodemographic characteristics and nutritional habits were determined through face-to-face interviews and through the use of questionnaires. The dTAC and dietary oxidative balance scores were calculated using a three-day dietary intake record. 8-OHdG levels were analyzed in the serum samples collected from the subjects. Results: Dietary ferric reducing antioxidant power (FRAP-1, FRAP-2), Trolox equivalence antioxidant capacity (TEAC), and oxygen radical absorbance capacity (H-ORAC) values were lower in patients with schizophrenia than in the healthy controls (P < 0.05). Serum 8-OHdG levels were found similar in both groups (P > 0.05). Conclusion: Nutritional interventions are needed in patients with schizophrenia given that insufficient antioxidant intake may increase oxidative stress, which in turn affects disease development. Therefore, healthy nutrition, especially sufficient intake of dietary antioxidants, should be encouraged in patients with schizophrenia.