Abstract Although social self-efficacy appears influential across a broad spectrum of human behaviour, existing adult measures of social self-efficacy have conceptual and psychometric limitations. The current research brought together the realms of trait social intelligence and self-efficacy to develop and evaluate a measure of social self-efficacy which for the first time included assessment of cognitive domains of social self-efficacy. Items were administered to 301 participants, along with measures of general self-efficacy, subjective wellbeing, social anxiety, depression, general anxiety, and stress. An exploratory factor analysis (Maximum Likelihood with Direct Oblimin extraction) revealed two interpretable factors that were labeled “Social Understanding Self-efficacy” (cognitive) and “Social Skill Self-efficacy” (behavioural). Construct and criterion validity were evident and internal consistency and test–retest reliability were good. It was concluded that the new 18-item measure has sound psychometric properties. As such, this measure may serve as a meaningful tool for researchers and clinicians. While theoretical and empirical frameworks informed the current research, given the exploratory nature of this study, future research should further investigate the psychometric properties of this measure using confirmatory factor analysis and by examining the predictive validity of this measure in a clinical context.