Research on self-assessment has overwhelmingly conceptualized it as a product and treated students as a homogeneous group, restraining our understanding of the topic. To address this gap, this study aimed to identify different student profiles based on their self-assessment and to examine how it related to their learning achievement over time. Quantitative data from 52 undergraduate interpreting students were analyzed using longitudinal cluster analysis and correlation analysis. Three distinct student profiles were identified: Active, Jumper, and Inactive. The Active Profile demonstrated a positive correlation between self-assessment and learning achievement, while the Jumper Profile showed a largely negative correlation, and the Inactive Profile showed volatile correlations. It is suggested that instructors should pay close attention to students in the Jumper Profile, as their self-assessment tends to fluctuate and may not be beneficial. Additionally, the findings highlight the importance of a process-based and person-driven approach to understanding self-assessment, which can help explore its complexity and recognize individual differences.