Purpose: To assess physical activity outcomes of a pedometer-based physically active learning (PAL) intervention in primary school children. Methods: Six paired schools were randomly allocated to either a 6-week teacher-led pedometer-based physically active learning intervention or a control (n = 154, female = 60%, age = 9.9 [0.3] y). Accelerometers assessed total daily sedentary time, light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA). Preintervention mean daily MVPA minutes grouped participants as Low Active (<45 min/d) and High Active (≥45 min/d). Results: From the final sample size, the intervention (n = 52) significantly improved LPA versus control (n = 31, P = .04), by reducing sedentary time. More intervention (+10%) than control (+3%) pupils met the 60 minutes per day guidelines. In both intervention subgroups, pupils spent less time in LPA (P < .05) versus control. The greatest nonsignificant increase was found in the Low Active pupils MVPA levels. Conclusions: Improvements in LPA were statistically significant in the intervention versus control group. In subgroup analysis, Low Active pupils in the intervention showed the greatest beneficial effects and the Most Active pupils may have replaced MVPA and sedentary time with LPA. The intervention group housed clusters of pupils showing variable responsiveness, justifying routine examination of subgroup variability in future studies.