This mixed methods study investigated how professional learning communities could support reformed teaching practices in the secondary science classroom. To assist preservice teachers with implementing these practices in the classroom, teachers must have a space for metacognitive reflection on their teaching practices (Darling-Hammond, 2006). Professional Learning Communities (PLCs) were utilized as a teacher reflection space in the present study. A PLC model, developed by the National Science Foundation Developing Leaders in Science Teaching (LIST) Noyce Track 2 program (Award #1660557), was used. PLC meetings were directed and guided by the preservice teacher. The LIST Collaborative PLC model consisted of four members: (a) an education specialist, (b) a university content specialist, (c) a secondary science cooperating teacher, and (d) a preservice secondary science teacher. Study participants included three preservice secondary science teachers receiving PLC support (experimental group) and three preservice secondary science teachers with no PLC support (control group). Data were collected by a pre- and post-semistructured interview, two classroom observations immediately followed by a debriefing session, two PLC meetings for the experimental group, and a pre- and post-Science Teaching Efficacy Belief Instrument (STEBI) survey. The Reformed Teacher Observation Protocol (RTOP), inquiry rate form, and Student Engagement Rate (SER) forms were used to collect data during classroom observations. Quantitative data were determined not statistically significant using Mann-Whitney and Wilcoxon signed rank tests, lending more credence to those findings. Findings indicated (a) preservice teachers’ definition of reformed teaching methods shifted across the study from “anything but direct instruction” to “student-centered teaching methods”; (b) hypothetically, participant mindset and buy-in were directly related to the amount of reformed teaching practices implemented in the classroom; (c) data revealed a lack of perceived support from Clinical Master Teachers (CMTs) and a valued, much-needed level of support provided by the PLCs; and (d) classroom observations and debriefing sessions, PLCs (experimental group), and university support (control group) were perceived as most impactful in supporting reformed teaching practices. Further longitudinal research is recommended to validate positive relationships between teacher growth mindset and PLC support for using reformed teaching practices in the secondary classroom by preservice secondary science teachers.