Team based learning (TBL) has emerged as a learning strategy in Korean medical schools since the early 2000s. However, there is a lack of research on the impact of TBL class on the academic achievement of medical students. This study aimed to examine the relationship between self-efficacy, team efficacy, engagement, perceived effectiveness, and academic achievement and identify factors that influence academic achievement in a medical school TBL class. The Cell Metabolism course was conducted in TBL for five weeks. This study involved 43 second-year premedical students in the Cell Metabolism course who signed the informed consent form and completed the survey. Data were collected using instruments that measured self-efficacy, team efficacy, engagement, effective perception, and academic achievement. Descriptive statistics, reliability tests, correlation analyses, and regression analyses were used to analyze the data. Results of the study showed that academic achievement in a medical school TBL class is positively associated with engagement and effective perception. Among these, engagement was identified as the primary factor influencing academic achievement, with more active student participation resulting in higher academic success. TBL are more meaningful as a team activity than as an individual activity. In the future, there is a need to explore different variables that can predict the effectiveness of TBL based on small group learning rather than teaching methods such as lecture.