The goal at this research is to study the effectiveness of a cognitive behavioral group therapy program in patients with Adjustment Disorder. The sample is made up of 102 patients from two Mental Health units and a Primary Care Center in Valencia (Spain). The treatment was a cognitive behavioral group intervention of one hour and a half session per week during eight weeks. Patients were evaluated at the beginning and end of the program. Monitoring was performed at three months. The resources used were: the Symptom Checklist-90-Revised (SCL-90-R), the Suicide Risk Scale (RS) and the SF-36 Health Survey (SF-36). The results show significant differences between previous and following treatment measures on key dimensions of the applied scales, maintaining these results at 3 months follow-up. The results suggest that cognitive-behavioral group therapy could be used as a first level of attention to Adjustment Disorder because of its effectiveness and efficiency.