As a critical component of second/foreign language learning, interpreting is both rewarding and highly anxiety-provoking. Yet, the review of the literature shows that studies on interpreting anxiety and other emotions are limited, and intervention studies on reducing interpreting anxiety and increasing confidence in interpreting are hardly available. This study employed a quasi-experimental design and explored the effects of technology-based practice on Chinese undergraduate English majors’ interpreting emotions and performance over a 12-week period. There were 44 students in the experimental group with technology-based practice and 46 were in the control group without technology-based practice from a university in Beijing. They took an interpreting test and answered an eight-item interpreting classroom anxiety scale, a nine-item interpreting classroom enjoyment scale, and a three-item interpreting self-efficacy scale prior to (phase 1) and after (phase 2) the intervention. The major findings were: (1) students in both groups became significantly less anxious and more joyful in the interpreting class, had significantly greater interpreting self-efficacy, and performed significantly better in the interpreting test in phase 2, (2) both groups started at a similar level in phase 1, and the experimental group reported a significantly lower interpreting classroom anxiety level, significantly greater interpreting self-efficacy, and higher interpreting test scores than the control group in phase 2, and (3) the learning modes significantly affected the participants’ interpreting classroom anxiety, self-efficacy, and performance. These findings indicate the effects of the intervention and hence enrich the current literature on interpreting emotions. The findings also highlight the importance of technology-based practice in enhancing students’ confidence, self-efficacy, and performance in interpreting, leading to sustainable development in interpreting competence.