Framed in teacher research, this article examines on how a group of 220 preservice language teachers' understandings of teacher agency evolved in a course on second language teaching curriculum. The participants were enrolled on a master's program on teaching English to speakers of other languages (TESOL), and data were gathered through course activities which included two surveys, reflective blogs, and an essay. Based on inferential statistics and qualitative content analysis, findings show that, with different degrees of confidence, the student-teachers believe that their projective (future) agency was harnessed through the course developing (1) willingness to use teacher agency as a tool for professional development and (2) willingness to use teacher agency as a drive to engage in critical teaching practices for multilingual settings. Drawing on a trans-perspective of language teacher agency, the study advances a model of projective teacher agency.