This research investigated the emergent discursive modes and their pedagogical functions found in model-based inquiry (MBI) science classrooms. A sample of four high school physics classrooms was video-recorded and analysed using a newly established discourse mode analysis framework. Qualitative methods were employed to identify the most salient types and sequences of discursive modes and to interpret their pedagogical functions in the context of MBI. Results indicated that exploring was one of the most frequently used discursive modes in the MBI classrooms. Sometimes two different types of exploring discourse were connected sequentially so that the pattern of "exploring" ("scientific phenomena")--"exploring" ("student ideas") appeared. The discursive sequences of "exploring"--"retrieving" and "exploring"--"negotiating" also emerged whereby the teacher guided students to align their models with the canonical knowledge of science. The teacher also helped students in modelling using "elaborating" and "reformulating" discourse modes as well as "metadiscourse." Although the MBI classes were implemented in a manner similar to teacher-guided inquiry, it was also observed that students participated actively in several discursive practices. Implications for model- or modelling-based science instruction and science education research were discussed. (Contains 1 table.)