Simulation is increasingly used to identify latent threats to patient safety, such as delays in recognition and management of time-sensitive conditions. The Rapid Cycle Deliberate Practice teaching method may facilitate "nano" (brief) in situ simulation training in a critical care setting to improve multidisciplinary team performance of time-sensitive clinical tasks. To determine whether nano-in situ simulation training with Rapid Cycle Deliberate Practice can improve pediatric intensive care unit team proficiency in identifying and managing postoperative shock in a pediatric cardiac patient. A quality improvement educational project was conducted involving nano-in situ simulation sessions in a combined pediatric and pediatric cardiac intensive care unit. The Rapid Cycle Deliberate Practice method was used with an expert-driven checklist for 30-minute simulation scenarios. A total of 23 critical care providers participated. The proportion of time-sensitive tasks completed within 5 minutes increased significantly from before to after training (52% [13 of 25] vs 100% [25 of 25]; P ≤ .001). Using a 5-point Likert scale, with higher scores indicating higher levels, the participants reported high degrees of performance confidence (mean, 4.42; SD, 0.20) and satisfaction with the simulation experience (mean, 4.96; SD, 0.12). The Rapid Cycle Deliberate Practice method was used to facilitate nano-in situ simulation training and identify areas requiring additional education to improve patient safety. In situ simulation can educate providers in a cost-effective and timely manner.