Recently, the intercultural approach, which aims to resolve social conflicts in multicultural societies through cultural encounters and dialogue, has been actively discussed. Intercultural education aims to foster smooth relationships and improve communication skills through interactions among various cultural groups. Analysis of previous studies has revealed the need for research on intercultural civic education programs targeted at adults. Therefore, this study was designed to develop an intercultural citizenship education program and to analyze its effects. For the study, previous research on interculturalism, intercultural citizenship education, and intercultural citizenship education programs was comprehensively analyzed. The developed intercultural citizenship education program was categorized into five major themes: understanding oneself and others, racism and hate speech, overcoming conflict and discrimination, breaking away from prejudice and stereotypes, and the future of our country. Subsequently, the program was implemented with 64 total second-year middle school students, 37 in the experimental group, and 27 in the control group, at an accredited lifelong educational institution in M City, South Jeolla Province. To analyze the effects of the education, an intercultural competency scale was used. The results showed that the intercultural citizenship education program for adult students was effective in conflict management, respect, communication, and reflection competencies, all at a statistically significant level. Finally, the authors compared the study results with previous research and discussed the findings. Findings indicated the necessity of enhancing multicultural citizenship awareness among adults and expanding teacher training in intercultural education. The program effectively improved intercultural competence among adult students, highlighting the importance of tailored educational content and active participation in discussions. Future research should ensure a balanced gender ratio among participants.