Abstract Background: Although the effectiveness of group cognitive-behavioral therapy (GCBT) has been studied, evidence is still not sufficient. Objective: The aim of the present study is to consider the effectiveness of GCBT with mood disorders and neurotic disorders. Methods: The present study assessed a total of 32 patients who were classified as F3 (mood disorders) or F4 (neurotic disorders) according to the ICD-10, and who attended GCBT sessions offered at The Tokai University Hospital. Depression and mood in these patients were assessed before and after GCBT by using the Center for Epidemiologic Studies Depression Scale (CES-D) and the Profile of Mood States (POMS). Results: A comparison of pre- and post-GCBT CES-D scores among all patients as well as within F3 and F4 groups showed a significant decrease in CES-D scores after GCBT. As for the POMS, a comparison of pre- and post-GCBT scores among all patients showed a significant improvement in “vigor” and “confusion” scores after GCBT. Discussion: The present study demonstrated that GCBT can relieve depression and improve some mood states. Furthermore, the GCBT sessions offered proved to be effective even when administered to a group of participants consisting of both mood disorders and neurotic disorder patients.