AIMS: To develop a simulation-based psychological first aid (PFA) education program for disaster relief workers and verify its impact on their PFA knowledge, PFA performance competence, and self-efficacy. BACKGROUND: Relief workers should be provided with systematic education on their required knowledge and skills; however, PFA training for relief workers is lacking, which results in ineffective mental health support during disaster situations. METHODS: This study adopted a non-equivalent control group pre-posttest quasi-experimental design. Thirty relief workers from mental health welfare centers in Seoul and Gyeonggi Province participated. The experimental group received a PFA lecture, a simulation-based PFA education program, and access to the Psychological Life Support (PLS) mobile application, which provides information on disaster situations and PFA techniques. The comparison group received a PFA lecture. The control group was provided with self-learning PFA materials. RESULTS: Among the three groups, the experimental group showed the greatest improvement in PFA knowledge, PFA performance competence, and self-efficacy from pretest to posttest, which was statistically significant. CONCLUSIONS: This study demonstrated the effectiveness of the simulation-based PFA education program combined with a PFA lecture and the PLS mobile app as complementary methods to assist relief workers in applying PFA in disaster situations.