Generalized Anxiety Disorder (GAD) is a chronic disease persisting for at least 6 months, characterized by excessive and continuous anxiety, which leads to evident problems and functional disorders. S100B is a glial protein that plays a role in intercellular communication regulating cell growth and differentiation, and intracellular signal transmission. This study aimed to analyze the serum S100B, 8-OHdG, and oxidative stress levels of patients newly diagnosed with GAD who had not started treatment, to better understand the underlying neurobiological basis of the etiology of GAD. Forty-four patients diagnosed with GAD according to DSM-5 diagnostic criteria and 44 healthy controls were included in the study. The Beck Anxiety Inventory (BAI) was used to determine the anxiety levels of the GAD patients. The serum S100B, 8-OHdG, total oxidant status (TOS), and total antioxidant status (TAS) levels were measured in the patient and control groups. The 8-OHdG values of the GAD group were determined to be statistically significantly higher than those of the control group (p=0.028). No significant difference was determined between the GAD patients and the control group in respect of the TAS, TOS, and oxidative stress index (OSI) values (p>0.05). The S100B levels of the GAD group were found to be higher than those of the control group. The results of this study showed that there could be DNA damage because of oxidative stress in GAD patients. There is a need for further studies to confirm the role of S100B protein in GAD etiology and pathogenesis.