We examined feasibility, acceptability, and benefits of a mindfulness-based relapse prevention (MBRP) intervention in a racially and ethnically diverse sample of 318 low-income women in substance use disorder treatment (2003-2006). The study used a single group, repeated measures design. Participant satisfaction was high (M = 3.4, SD = .3), but completion was modest (36%). Linear regressions examining change in addiction severity and psychological functioning by dosage showed that higher dosage was associated with reduced alcohol (β = -.07, p < .05), drug severity (β = -.04, p < .05), and perceived stress (β = -2.29, p < .05) at 12 months. Further research on MBRP efficacy for this population is warranted. The study's limitations are noted.