Objective: The aim of this study was to evaluate the relationship between apelin-36 and oxidative parameters and Generalized Anxiety Disorder (GAD). Apelin which prevents hippocampal neuron death is an endogenous ligand for G protein-bound APJ receptors in the central nervous system. Oxidative Stress occurred by free radicals which caused apoptosis in the hypothalamus, hippocampus and amygdala regions of the CNS. Methods: In this study, 61 patients diagnosed with generalized anxiety disorder at psychiatry polyclinic and 55 healthy subjects were enrolled. The Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I) and the Hamilton Anxiety Rating Scale (HARS) were used in this study and they were filled by the patients and healthy individuals. Serum apelin-36 level was measured by using an ELISA kit. TAS and TOS in the serum was measured by an automated system. The data wereanalyzed by using the SPSS. Results: It wasfound that serum apelin-36, TOS and OSI levels were significantly lower in patients group than controls. In addition, negative correlation was detected between apelin 36 levels and HARS scores, TOS and OSI values in patients group.TAS values were found as similar between the patient and control group.There was no correlation between TAS and Apelin 36 in the patient group. Conclusion: In this study it is found that serum apelin-36, TOS and OSI levels were low in GAD. According the results, Apelin-36 and oxidative stress may play a role in the etiopathogenesis of Generalized Anxiety Disorder.