Introduction Two-thirds of people living with HIV (PLWH) show sub-optimal adherence to antiretroviral therapy (ART) and one-third engages in risky sex. Both non-adherence and risky sex have been associated with emotional distress and impulsivity. To allay distress and lessen impulsivity, mindfulness training (MT) can be helpful. In this trial, we will investigate the utility of phone-delivered MT for PWLH. The primary outcomes comprise feasibility and acceptability of phone-delivery; secondary outcomes are estimates of efficacy of MT on adherence to ART and safer sexual practices as well as on their hypothesized antecedents. Methods/design Fifty participants will be enrolled in this parallel-group randomized clinical trial (RCT). Outpatients recruited from an HIV treatment clinic will be randomized (1:1 ratio) to either MT or to an attention-control intervention; both interventions will be administered during 8 weekly phone calls. ART adherence (self-reported measure and unannounced phone pill counts), sexual behavior (self-reports and biomarkers), mindfulness, depression, stress, and impulsivity will be measured at baseline, post-intervention, and 3 months post-intervention. Conclusions MT has great potential to help PLWH to manage stress, depressive symptoms, and impulsivity. Positive changes in these antecedents are expected to improve safer sex practices and ART adherence. If results from this exploratory trial support our hypotheses, we will conduct a large RCT to test (a) the efficacy of MT on ART adherence and safer sex practices and (b) the hypothesis that improved ART adherence and safer sex will reduce viral load, and decrease the incidence of sexually transmitted infections, respectively.