This research aims to analyze and investigate the rhetorical patterns used by undergraduate ELT students in writing the introductory section of thesis proposals. This study focuses on the rhetorical structures (rhetorical moves) used by the students, in particular how the argumentation and rhetorical patterns of thesis proposal writing are adopted by the students. This study uses a mixed sequential explanatory method, which investigates the rhetorical patterns used by students quantitatively through text analysis and continues with descriptive analysis using the Project Justifying Model (PJM) adapted from Swales’ CARS. From the investigation and discussion, it was found the tendencies (general patterns) used by students in the introduction to confirm the previous studies to set the niche of their thesis proposals. The results corroborate the lack of rationale to argumentation, e.g. urgency and rationale upon the research proposal. The findings are expected to become the basis for the supervisory approach to ELT students in writing research proposal.