Objective <p>This study investigated serum Brain-Derived Neurotrophic Factor (BDNF) levels and the BDNF rs6265 (Val66Met) polymorphism in patients with anxiety disorders compared to healthy controls, and examined their relationship with symptom severity to clarify their role in anxiety etiology.</p> Methods <p>The study included 64 patients diagnosed with anxiety disorders and 64 healthy controls. Clinical assessments were performed using the Hamilton Anxiety Rating Scale (HAM-A), Hospital Anxiety and Depression Scale (HADS), and Level 2 Somatic Symptom Scale. Serum BDNF levels were measured using ELISA, and rs6265 polymorphism genotyping was performed via RT-PCR.</p> Results <p>Median serum BDNF levels were significantly lower in the patient group compared to controls [1.50 (0.19–3.28) ng/mL vs. 1.62 (1.05–9.50) ng/mL; <i>p</i> = 0.007]. Significant negative correlations were found between serum BDNF levels and scores on the HAM-A (<i>rs</i>= -0.386), HADS (<i>rs</i>= -0.317), and Level 2 Somatic Symptom Scale (<i>rs</i>= -0.224) (<i>p</i> &lt; 0.01 for all). ROC analysis identified a BDNF cutoff value of 1.54 ng/mL for predicting anxiety disorders (sensitivity: 59.4%, specificity: 57.8%, AUC: 0.639; 95% CI: 0.544–0.735). No significant differences were observed between groups regarding Val66Met genotype distribution (<i>p</i> = 0.843), nor was there a significant association between the polymorphism and serum BDNF levels (<i>p</i> = 0.215).</p> Conclusion <p>Our findings demonstrate that decreased serum BDNF levels are associated with the presence and symptom severity of anxiety disorders. However, the Val66Met polymorphism does not appear to be a primary determinant of serum BDNF levels in this population, suggesting that other genetic or environmental factors may be involved.</p>