Some findings have emerged from the field of oxidative stress in patients with psychiatric disorders. These date also state that oxidative balance and obsessive-compulsive disorder (OCD) are significantly related. Yet, researchers have not investigated oxidative stress, oxidative balance, and DNA damage together. We tested the levels of paraoxonase-1 (PON1), and arylesterase (ARE). We also tested the dipeptidyl peptidase-IV (DPP-IV), oxidative stress, and oxidative DNA damage. We enrolled 37 patients with OCD in the study. The diagnosis of OCD according to DSM-V criteria was established. Patients had not received treatment for at least 6 months. The controls were matched with the patients about sex, age, body mass index (BMI), and smoking. Clinicians used the sociodemographic information form. All subjects were evaluated with a semi-structured questionnaire. Serum PON1, ARE, DPP-IV, oxidative stress index (OSI), and 8‑hydroxideoxiguanosine (8-OHdG) calculations were conducted in the biochemical laboratory. PON1 and DPP-IV levels were not different between OCD patients and the control group (P > 0.05). An oxidative DNA damage marker 8-OHdG—and OSI were higher in the patient’s group (p < 0.05). But levels of ARE were significantly lower in OCD patients (P < 0.05). We found evidence that oxidative stress-induced parameters such as OSI, ARE, and 8-OHdG might be related to a specific pathologic state in patients with OCD. The findings may provide a rationale for treating the pathological processes.