Interpreting Self-Efficacy (ISE) is the belief one holds about their own interpreting capabilities. One of the first instruments to measure this self-belief is S.-B. Lee's ISE scale, a statistically sound self-report questionnaire designed to measure the ISE levels of undergraduate students majoring in consecutive interpreting (Cronbach's a = 0.896). In theory, this scale helps to predict how successful a student will be in an interpreting task. The present study aims to show whether there is a strong correlation between ISE and actual performance among undergraduate students. For this purpose, the study was conducted in three steps. First, the ISE scale was administered to 33 undergraduate students enrolled in an advanced course on consecutive interpreting, in order to measure the students' ISE levels. Second, the students' interpreting performances were assessed on multiple occasions, using triangulation involving three different assessor groups, namely the classroom teacher, peer students, and external raters. Third, statistical analysis was performed to find out whether there is a relationship (and what kind of relationship exists) between the students' ISE and performance levels. Findings from this study and their implications for interpreter training are also discussed.