A number of people with HIV participated in a 48-hour cognitive behavioral group intervention, divided into four monthly workshops. Twenty-six participants started the program and 18 completed it and responded at the four-month follow-up. After treatment, significant improvement was achieved in declared stigma, internalized stigma, depression, and state anxiety. All these improvements were maintained at the follow-up measurement four months later, with trait anxiety also improving in this last measure. Participants’ results were compared with an HIV control group. Twenty-four respondents completed the first test battery and 16 completed the last. The evolution of this group was assessed, as well as the differences between both groups at three time points: pre-intervention, post-intervention, and follow-up. Intragroup and inter-group comparisons were examined with the Student t-tests for related samples and for independent samples respectively. In addition, the effect size was calculated for each comparison. The results support the efficacy of the group intervention presented.