A dependent group contingency strategy called Fair Play Game was applied to promote increase in number of steps during physical education classes for sixth-grade students. Results from a multiple baseline design across three classes showed that the mean number of steps for baseline vs. intervention were: Class 1: 43 vs. 64 steps/minute; Class 2: 49 vs. 81 steps/minute; Class 3: 50 vs. 87 steps/minute. Visual inspection of the graphs showed that Class 1 had an upward trend of number of steps (baseline vs. intervention) without a change in level. Classes 2 and 3 demonstrated clearer change in level of number of steps between these two phases. Social validity data showed that students increased their engagement in class and Fair Play Game is a feasible and acceptable strategy. Therefore, it can be concluded that Fair Play Game appeared to be associated with students' increase in active behaviours in physical education lessons.