Many have examined game-based instructional models, though few have examined the effects of the Tactical Games Model (TGM) on secondary-aged students. Therefore, this study examined the effects TGM has on secondary students' physical activity (PA) and gameplay performance (GPP) in three secondary schools. Physical education teachers (N = 3) were trained extensively on the TGM; they then implemented 10 TGM lessons derived from the Tactical Games Approach textbook (Mitchell, Oslin, & Griffin, 2013) to secondary students (N = 123). Pedometers and Team Sports Assessment Procedure (TSAP) were used to measure students' PA levels and pre- and post-GPP, respectively. Fidelity was determined by Metzler's (2005) benchmarks for TGM and measured that teachers implemented TGM the majority of the time (93.5%). A one-way ANOVA and subsequent post hoc analysis found a significant difference between the average number of steps students took across all lessons for Teacher 1 (soccer; M = 60.7, SD = 17.5) and Teacher 2 (football; M = 55.8, SD = 20.0); Teacher 3 (handball) was not significantly different (M = 55.2, SD = 20.0). An independent t test examined step counts between gender, and repeated measures "t" tests examined GPP pre- and posttest scores. Secondary-aged females averaged significantly higher steps (M = 61.3, SD = 14.1) than secondary-aged males (M = 51.6, SD = 11.1). All GPP pre- and postmeasures were significantly different (p < 0.01) and indicated a significant improvement in GPP. TGM generated positive physical effects on secondary students. Although students were slightly missing the recommended 50% of class time in moderate to vigorous PA, the quality of moderate to vigorous PA or physical education learning indices should be considered.