Purpose: The purpose of this study was to develop a multimedia learning program for patients with diabetes mellitus (DM) diet education using standardized patients and to examine the effects of the program on educational skills, communication skills, DM diet knowledge and learning satisfaction. Methods: The study employed a randomized control posttest non-synchronized design. The participants were 108 third year nursing students (52 experimental group, 56 control group) at K university in Seoul, Korea. The experimental group had regular lectures and the multimedia learning program for DM diet education using standardized patients while the control group had regular lectures only. The DM educational skills were measured by trained research assistants. Results: The students who received the multimedia learning program scored higher for DM diet educational skills, communication skills and DM diet knowledge compared to the control group. Learning satisfaction of the experimental group was higher than the control group, but statistically insignificant. Conclusion: Clinical competency was improved for students receiving the multimedia learning program for DM diet education using standardized patients, but there was no statistically significant effect on learning satisfaction. In the nursing education system there is a need to develop and apply more multimedia materials for education and to use standardized patients effectively.