The present study evaluated the efficacy of a group therapy program in improving psychosocial adjustment to HIV infection, and tried to identify variables predictive of greater improvement. The outcome of 47 completing patients was analyzed, comparing the measures between T1 (1 month before therapy), and T2 (first session), and between T2 and T3 (last session) using the Wilcoxon matched-pairs signed-ranks test for each dimension of the Psychosocial Adjustment to Illness Scale (PAIS). The therapy consisted of 16 weekly 2-hour sessions following a structured time-limited cognitive-behavioral group psychotherapy program. During the intervention (between T2 and T3) a significant improvement was observed in health care orientation, vocational environment, domestic environment, sexual relation, extended family relationships, social environment, and total PAIS. There were no changes during baseline (between T1 and T2) in any of the PAIS subscales, or in the total PAIS score. Sexual route of transmission was independently associated with an improvement in health care orientation (β = 2.525). Time since HIV diagnosis (β = 0.022) and being employed (β = 2.548) were independently associated with an improvement in adjustment to vocational environment. Men who have sex with men showed a poorer improvement in adjusting to family relations after the intervention (β = −2.548). Finally, a lower CD4 count (β = −0.005) and being employed (β = 3.054) were independently associated with an improvement in adjustment to social environment. Our psychotherapy program improved psychosocial functioning in a heterogeneous sample of HIV-1-infected patients referred to a consultation-liaison psychiatry unit.