This study aims to find out whether there is a significant relationship between Interpreting Self-Efficacy (ISE) and translation/interpreting performance levels. For this purpose, 144 undergraduate students at a Seoul-based university (74 translation students and 70 interpreting students) were asked to fill in Lee`s (2014) ISE questionnaire, and their responses (i.e. ISE scores) were then statistically compared with their translation and interpreting performance scores (summative assessment scores assigned by one translator trainer and three interpreter trainers). The analysis shows that there are strong positive correlations between ISE and interpreting performance scores, while there are no significant correlations between ISE and translation scores.