Self-assessment and reflective thinking (RT) can arm learners to monitor and evaluate their learning progress. Despite the long history of the core of self-assessment (CSA) and RT, little is known about how they may contribute to learner enjoyment (LE) and learner immunity (LI). Therefore, the current research attempted to propose a model to depict the interplay among CSA, RT, LE, and LI. To this end, the Core of Self-Assessment Questionnaire (CSAQ), Reflective Thinking Questionnaire (RTQ), Foreign Language Enjoyment Scale (FLES), and Language Student Immunity Instrument (LSIS) were administered to 518 Iranian EFL university students. The results of confirmatory factor analysis (CFA) and structural equation modeling (SEM) indicated that EFL university students with higher levels of CSA and RT skills experienced more enjoyment and were immunized productively. Furthermore, the critical role of RT in CSA was discovered. The implications of this study may unveil new prospects for implementing learning-oriented assessment in the classroom and RT practices in educational programs.