This mixed-methods study uses concept maps to investigate the effects of an English pedagogical grammar course on the beliefs of teachers-in-training (n = 40) enrolled over a 2-year period at a private university in the U.S. Midwest. The course takes a functional approach to grammar based on systemic-functional linguistics and is typically the first exposure to functional grammar that these teachers-in-training experience with either their own language learning or prior coursework. As a result, this study was designed to explore the extent to which participants integrate this approach with their pre-course beliefs. Analysis of participants' pre-course concept maps indicates that they mainly believe grammar to consist of structures at the word and morpheme levels. Quantitative comparisons of pre- and post-course concept maps reveal that this belief continues to hold even as participants show much growth in knowledge about grammar at the sentence and discourse levels. An in-depth qualitative analysis of maps from a subset of participants (n = 7) shows that only two substantially shifted their beliefs about teaching grammar functionally. The findings have practical implications for course design and overall programme design in language teacher education programmes.