To better understand the relationship between abstinence self-efficacy and treatment outcomes in substance use disorder patients, experts in the field need more information about the levels of abstinence self-efficacy most predictive of treatment outcomes. Participants (N = 2,967) from 15 residential substance use disorder treatment programs were assessed at treatment entry, discharge, and 1-year follow-up. A signal detection analysis compared the ability of different measures of self-efficacy to predict 1-year abstinence and identified the optimal cutoffs for significant predictors. The maximal level of abstinence self-efficacy (i.e., 100% confident) measured at discharge was the strongest predictor of 1-year abstinence. Treatment providers should focus on obtaining high levels of abstinence self-efficacy during treatment with the goal of achieving 100% confidence in abstinence.