In this study examining the effectiveness of Metacognitive Therapy in Generalized Anxiety Disorder, a nine-session therapy process was conducted with a client, and the Worry Beliefs Scale and Beck Anxiety Scale were used as measurement tools. According to the findings, Metacognitive Therapy was found to be effective in the treatment of Generalized Anxiety Disorder. The study is a case report and there is a need for further studies to be conducted with more than one client and to test the effectiveness of Metacognitive Therapy comparatively.