Students’ success is one of the foremost objectives in higher education, and their self-efficacy plays a prominent role in students’ achieving their full potentials. It is especially important in STEM fields, which often suffer from higher attrition rates. Therefore, it is important to understand students’ self-efficacy levels at an early stage in an effort to retain students and enhance diversity. In this study, we look at the self-efficacy of students participating in a first-year introductory CS class and analyze the trends over the course. We also study the demographic differences across gender and class standing with regard to self-efficacy. Lastly, in a succession of research questions, we ask and answer the question of whether the adoption of a new platform to streamline the students’ experience with peer reviews on assignments in the course is justified. We do not find a difference in self-efficacy among students of different gender. However, we do find that freshmen students begin with lower self-efficacy than sophomore students, and the self-efficacy of freshmen students con-sistently improves after each peer review. While peer review in first-year courses may improve the self-efficacy of some students, the data from the use of a new peer-review platform in this study suggests that more research needs to be conducted before using the tool’s automated grading system in a first-year computer science course.