INTRODUCTION: The impact of booster training on pediatric resuscitation skills is not well understood. Rapid cycle deliberate practice (RCDP) to supplement pediatric advanced life support (PALS) training is beginning to be used to improve resuscitation skills. We tested the impact of booster RCDP training performed at 9 months after initial RCDP training on pediatric resuscitation skills of pediatric residents. OBJECTIVE: This study evaluated the impact of a 9-month RCDP booster training on PALS skills compared with usual practice debriefing (plus/delta) after an initial RCDP training session for PALS-certified pediatric interns. METHODS: All pediatric interns at a single institution were invited to a 45-minute RCDP training session after their initial PALS certification. The PALS performance score and times for key events were recorded for participants immediately before and after the RCDP training as well as 6, 9, and 12 months after the RCDP training. Learners were randomized to an RCDP intervention and usual practice (plus/delta) group. The intervention group received booster RCDP training after their 9-month assessment. RESULTS: Twenty eight of 30 residents participated in the initial training with 22 completing randomization at 9 months. There was no significant difference in 12-month PALS median performance scores after the booster training between the intervention and usual practice groups (83% vs. 94%, P = 0.31). There was significant improvement in PALS performance score from 51 ± 27% pre-initial RCDP assessment to 93 ± 5% post-initial RCDP training (P < 0.001). There were significant improvements in individual skills from pre- to post-initial RCDP testing, including time to verbalize pulseless, start compressions, and attach defibrillation pads (P < 0.001). CONCLUSIONS: Rapid cycle deliberate practice booster training versus plus/delta training at 9-month post-initial RCDP training did not alter 12-month performance. However, RCDP is effective at improving PALS performance skills, and this effect is maintained at 6, 9, and 12 months. Our study supports the importance of supplemental resuscitation training in addition to the traditional PALS course.