This study aims to analyze the characteristics and areas for improvement of a long-running non-formal multicultural teacher education program implemented at an elementary teacher training institution. To this end, a collaborative autoethnography was conducted, focusing on the case of the Multicultural Seminar program, which has been offered as a non-formal curriculum at C University of Education. The main findings are as follows. First, the program was embedded within the university’s official organizational structure, enabling the development of a stable operational system. Second, in terms of planning and implementation, the program ensured content diversity and enhanced the quality of teaching strategies through a collaborative decision-making process involving professors from diverse academic backgrounds. Third, in terms of content, the program expanded the scope of diversity addressed in multicultural teacher education beyond race and ethnicity to include social class, disability, labor, generation, gender identity, and education. Fourth, in terms of teaching methods, a range of multicultural media—including films, documentaries, and literature—was used to provide opportunities for prospective teachers to engage with other cultures. Structured instructional guidance supported in-depth discussion and cultural reflection. However, due to the nature of non-formal curricula, challenges remain in fostering voluntary participation among prospective teachers and enhancing instructors’ competencies. Based on these findings, the study presents practical implications for the effective operation of non-formal multicultural teacher education programs in elementary teacher training institutions and identifies directions for further academic inquiry.