This study is aimed at investigating the rhetorical structure of Introduction chapters of English master theses written by Indonesian postgraduate students and identifying the frequency of communicative moves and their constituent steps as well as finding how the students justify their research projects reported in their Introduction chapters. The research design was mixed method research combining quantitative and qualitative method. Twenty Introduction chapters of English master theses were taken from two different fields; English language education and applied linguistics, and they were analyzed using checklists. The results: (1) three moves and fifteen steps are found in the introduction chapters of master theses and three newly identified steps other than those specified in Bunton's are also found in the corpus of this study and (2) three moves are considered obligatory moves, seven steps are classified as obligatory, four Steps are conventional and seven Steps are optional. Further, the majority of Indonesian postgraduate students tend to rhetorically justify their research project based on the knowledge gap found in the literature. This study concludes that the move and step model suggested by Bunton (2002) and modified from Swales' CARS is effective enough to capture the possible rhetorical structure of introduction chapter of master thesis written by Indonesian postgraduate students.