AIM: This study aims to develop the Mobile Simulation Program for Nursing Delegation (MSP-D) to enhance nurses' delegation skills and evaluate its effects on nurses' preparedness to delegate, critical thinking disposition and role ambiguity reduction. BACKGROUND: Effective delegation is crucial for optimal patient care in nursing practice. However, many Korean nurses with insufficient delegation training in a new nursing model where they collaborate with nursing assistants. DESIGN: A randomised controlled trial with a pre-post-test design. PARTICIPANTS AND SETTING: The participants were 96 nurses from three general hospitals in South Korea, randomly assigned to either the experimental (n = 48) or control group (n = 48). METHODS: The MSP-D is a mobile web-simulation and the experimental group used the MSP-D for three weeks. Data were collected pre- and post-intervention. The study was registered with the Clinical Research Information Service (KCT0007516) on 19 July 2022, with recruitment beginning on 20 August 2022. RESULTS: The experimental group showed significant improvements in preparedness to delegate (p <
0.001), critical thinking (p = 0.038) and decreased role ambiguity (p = 0.041). compared with the control group. Debriefing analysis revealed that participants' reflections aligned with the learning objectives, indicating the study's educational goals were met. CONCLUSION: The MSP-D is an effective educational tool for improving nurses' delegation skills and may enhance job training for nurses collaborating with nursing assistants to improve nursing care quality in a new nursing delivery model. Mobile simulation education significantly improves effectiveness due to its high accessibility and flexibility.