Self-efficacy to remain abstinent in high-risk situations is associated with better outcomes post-treatment among individuals with substance use disorders (SUD). It is therefore important for researchers and clinicians to have valid and reliable measures to assess this construct. In the present study, we evaluated the psychometric properties of the Brief Situational Confidence Questionnaire (BSCQ) within a large clinically mixed SUD treatment population. Participants were adult patients (N = 1384) who entered an inpatient SUD treatment program in Guelph, ON, Canada. As part of routine clinical assessment, participants completed the BSCQ, as well as measures of confidence to stay abstinent, craving, and frequency and severity of substance use. Confirmatory factor analysis indicated that a bifactor model was the best fit to the data, with the general factor accounting for the vast majority of the variance in scores. Bifactor indices also suggested that the BSCQ was best conceptualized as unidimensional despite the presence of some multidimensionality. Tests of measurement invariance demonstrated configural, metric, and scalar invariance across age, gender, ethno-racial identity, and substance use disorder subgroups. The BSCQ exhibited convergent and concurrent validity via associations with general confidence to remain abstinent, less frequent substance use, and fewer cravings. Scores on the BSCQ were also significantly lower among individuals with a severe SUD. The findings provide evidence that the BSCQ is a psychometrically sound measure for assessing situational self-efficacy in an SUD treatment population, supporting its clinical utility.