The purpose of this study is to investigate the effect of Technological Pedagogical Content Knowledge (TPACK) Game activities supported micro-teaching practices on middle school preservice mathematics teachers' TPACK self-efficacy perception levels. A single group pretest-posttest experimental design was employed. One hundred middle-school preservice mathematics teachers, attending a mathematics instruction course, participated in the study. The Technological Pedagogical Content Knowledge Survey (?ahin, 2011) was used to determine teachers' level of TPACK-measured self-efficacy. One-way Repeated Measures ANOVA was performed to analyze possible differences between teachers' pre and post self-efficacy scores. The result of this analysis demonstrated a statistically meaningful difference for the overall survey as well as for all dimensions of it. These findings suggest that micro-teaching practices do indeed increase preservice teachers' TPACK self-efficacy perception scores. [Paper presented at the International Instructional Technologies & Teacher Education Symposium (ITTES 2018) (Edirne, Turkey, September 12-14, 2018).]