Background: Simulated critical care training, when complemented by structured debriefing that addresses affective, psychosocial, and cognitive domains, provides a solid foundation for developing critical thinking and decision-making skills among nursing students. Structured debriefing serves not only as a mechanism for reflective practice but also as an evidence-based instructional methodology that optimizes experiential learning. This study aims to evaluate the impact of structured debriefing conducted post-simulation, on the acquisition and development of essential nursing competencies in undergraduate students. Methods: A descriptive cross-sectional study with a quantitative design was conducted, involving a cohort of 71 fourth-year nursing students enrolled in the curricular unit “Critical Care Nursing”. The sample comprised a single class that participated in two high-fidelity clinical simulation sessions, each immediately followed by a structured debriefing session. After each simulation, students completed the Debriefing Assessment Scale Associated with Simulation (EADaS), which evaluates three domains of the debriefing experience: affective, cognitive, and psychosocial. Results: Students expressed an overall positive perception of the debriefing sessions. In the first evaluation, the affective dimension received the highest mean score (4.687), despite some variability in individual responses. By the second evaluation, the cognitive dimension attained the highest score (4.668), suggesting an enhanced perception of knowledge integration. Both cognitive and psychosocial dimensions demonstrated marked improvement between the two assessment moments. Conclusions: The findings underscore the essential role of structured debriefing in simulated critical care training, particularly in fostering emotional safety, critical reflection, and interpersonal competence. As such, structured debriefing stands out as a vital pedagogical approach in preparing nursing students to become confident, competent, and reflective practitioners, thereby contributing to improved patient safety and care outcomes.