Inpatients involuntarily committed to a chemical dependency unit and exhibiting a co-occurring depressive disorder received either individual sessions of acceptance and commitment therapy (ACT) or treatment as usual (TAU) within the context of an ongoing 12-step program. Results indicated significant, but equivalent, reductions in levels of depression for both treatment conditions. However, participants randomly assigned to receive ACT (n = 12) required a shorter treatment phase and smaller dose of individual therapy to meet criteria for discharge compared to their TAU counterparts (n = 12). As expected, an analysis of the therapeutic process suggested that a differential reduction in levels of experiential avoidance associated with ACT may have contributed to its apparent relatively greater therapeutic impact. Limitations of the study, as well as its possible implications for the treatment of comorbid depression and alcohol use disorders in particular, and of co-occurring presenting clinical problems in general, are discussed.