Students completing undergraduate thesis projects rely on supervisory feedback to improve their academic writing and research abilities. Despite its critical role, supervisory feedback on undergraduate theses is under-researched. Adopting a qualitative multiple case-study approach, this study explores how students' motivation for writing the undergraduate thesis and English proficiency might influence their engagement with supervisory feedback. Four students participated in the research through purposive sampling. Multiple sources of data were collected from the focal participants, including stimulated recalls, interviews, and focal students' thesis drafts. The findings suggested that students' motivation for writing their undergraduate thesis and English language proficiency played pivotal roles in the extent and manner of their engagement. Pedagogical implications derived from the findings are discussed to enhance undergraduate thesis supervision quality in the Chinese tertiary context.