||This study investigates the construct of Teacher Language Awareness (TLA) in a group of preservice mainstream K-12 teachers who are developing skills to work with English Language Learners (ELLs) in United States (US) public school contexts. Specifically, the study seeks to explore how preservice teachers' participation in directed university coursework about second language (L2) instruction affects the development of TLA. Participants in this quasi-experimental study (N=116) derive from two groups: one group enrolled in a course that adopted an incidental approach to the development of TLA, and the other enrolled in a course that adopted an deliberate approach. The study established a descriptive baseline for the participants' TLA via pretest tasks in the Analyst and Teacher Domains. Participants' degree of TLA before directed coursework was low, based on their pretest scores on Analyst and Teacher Domain tasks, as well as analysis of written reflections. Yet, participants from the deliberate group who received treatment in the form of an explicit approach to the development of TLA exhibited a significant improvement in the Analyst Domain over those enrolled in the incidental TLA course. Neither group demonstrated significant improvement in the Teacher Domain. Focus group interviews were conducted with participants from both groups to determine how their attitudes, perceptions, and experiences might have influenced their TLA development during the semester. The results suggest that deliberate approaches to developing knowledge about language (KAL) are necessary for K-12 mainstream teachers. Results also suggest that teacher educators may need to adopt an explicit approach to developing TLA in L2 methods classes in order to help PSTs integrate TLA as a critical component of their pedagogical content knowledge.