BACKGROUND: While the learning outcomes of observational learning in simulation-based experiences have been documented, there is a paucity of studies that have provided evidence of the efficacy of observational learning in influencing reaction, performance, and behavioral changes. PURPOSE: This study aimed to assess the efficacy of structured observational learning on the learning outcomes of nursing students in delirium care simulations. METHODS: A parallel-group randomized trial design was employed. Nursing students were randomly assigned to either the observational learning group (n = 20) or the active participant group (n = 20). Participants completed a web-based self-administered questionnaire assessing psychological safety, clinical reasoning skills, and learning transfer. Performance in simulations was evaluated by raters. Data were analyzed using paired t-tests and two-sample t-tests. RESULTS: Both observers and active participants demonstrated improvements in psychological safety and clinical reasoning skills following the simulation-based experiences. Notably, students in the observational learning group exhibited significantly higher performance and learning transfer compared to those in the active participant group. CONCLUSION: Structured observational learning significantly enhanced learning outcomes related to reaction, performance, and behavior in nursing students. Further research is required to explore the impact of reflective observation on the acquisition and retention of competencies in simulation-based learning environments.