The primary objective of this study was to evaluate the efficacy of a pilot intervention using a game-centered approach for improvement of physical activity (PA) and physical education (PE) outcomes simultaneously, and if this had an impact on enjoyment of PE. A group-randomized controlled trial with a 7-week wait-list control group was conducted in one primary school in the Hunter Region, NSW, Australia. Participants (n = 107 students; mean age = 10.7 years, SD 0.87) were randomized by class group into the Professional Learning for Understanding Games Education (PLUNGE) pilot intervention (n = 52 students) or the control (n = 55) conditions. PLUNGE involved 6 × 60 min PE lessons based on game-centered curriculum delivered via an in-class teacher mentoring program. Students were assessed at baseline and 7-week follow-up for fundamental movement skills (FMS) of throw and catch, game play abilities of decision making, support and skill performance; in-class PA; and enjoyment of PA. Linear mixed models revealed significant group-by-time intervention effects (p < 0.05) for throw (effect size: d = 0.9) and catch (d = 0.4) FMS, decision making (d = 0.7) and support (d = 0.9) during game play, and in-class PA (d = 1.6). No significant intervention effects (p > 0.05) were observed for skills outcome during game play (d = -0.2) or student enjoyment (d = 0.1). Game-centered pedagogy delivered via a teacher professional learning program was efficacious in simultaneously improving students' FMS skills, in-class PA and their decision making and support skills in game play.