{Reference Type}: Journal Article {Title}: The effect of classroom-based assessment (CBA) on Chinese EFL learners' speaking performance, engagement, and willingness to communicate: Undergraduate students' perceptions. {Author}: Liu Y; {Journal}: Heliyon {Volume}: 10 {Issue}: 12 {Year}: 2024 Jun 30 {Factor}: 3.776 {DOI}: 10.1016/j.heliyon.2024.e32629 {Abstract}: CBA has emerged as a prominent pedagogical approach aimed at intertwining assessment within the instructional process, effectively fostering student learning. In English as a Foreign Language (EFL) education, CBA has garnered considerable attention, given its potential to enhance language learners' engagement, speaking proficiency, and willingness to communicate. This mixed-method research study delves into the impact of Classroom-Based Assessment (CBA) on the speaking performance, engagement, and willingness to communicate of undergraduate Chinese EFL learners. The study involved 90 Chinese EFL learners in the quantitative phase and 25 in the qualitative phase. Data collection comprised three questionnaires and an interview checklist. The data analysis employed inferential statistics (t-tests) for the quantitative data and thematic analysis for the qualitative insights. The findings of this study reveal that CBA exerts a significant influence on language learners' engagement, speaking abilities, and willingness to communicate. The quantitative results, as indicated by t-tests, indicate noteworthy improvements in these key aspects when CBA is integrated into the classroom environment. Moreover, the qualitative phase of the study, employing thematic analysis, uncovered five distinct ways through which CBA impacts the main variables under investigation. This research elucidates the multifaceted influence of CBA on undergraduate Chinese EFL learners. It not only demonstrates the quantitative impact on engagement, speaking skills, and willingness to communicate but also offers valuable qualitative insights into the diverse ways through which CBA enhances the language learning experience. These findings underscore the significance of integrating CBA into EFL classrooms as a potent tool for optimizing learner outcomes.