Mounting evidence suggests that smokers living with HIV/AIDS have a significantly increased risk of numerous adverse health outcomes (both AIDS- and non-AIDS-related) compared with HIV-positive nonsmokers. Therefore, efforts to design and implement effective cessation programs for this ever-growing special population are warranted. The present study assessed the effects of a cell phone intervention (CPI) on hypothesized mediators (i.e., changes in depression, anxiety, social support, and self-efficacy) demonstrated to influence cessation outcomes in other populations. Ninety-five participants from an inner-city AIDS clinic were randomized to receive either the CPI or recommended standard of care (RSOC) smoking cessation treatment. Participants randomized to the RSOC group (n=47) received brief advice to quit, a 10-week supply of nicotine patches, and self-help materials. Participants randomized to the CPI group (n=48) received RSOC components plus a series of eight proactive counseling sessions delivered via cell phones. A series of regression analyses (linear and logistic) was used to assess the relationships between treatment group, the hypothesized mediators, and biochemically confirmed smoking cessation outcomes. Results indicated that the CPI group experienced greater reductions in anxiety and depression, and increases in self-efficacy compared with the RSOC group. Further, changes in depression, anxiety, and self-efficacy weakened the association between treatment group and cessation outcome. The mediator hypothesis, however, for social support was rejected, as the difference score was not significantly associated with treatment group. These results suggest that the efficacy of the CPI is at least partially mediated by its ability to decrease symptoms of distress while increasing self-efficacy.