International Cultural Immersion Experience (ICIE) is becoming a common pedagogical practice that prepares counselor-trainees to effectively work with diverse clients. This quantitative study evaluated the effect of ICIE, which is based on the current immersion best practices, on the development of trainees’ multicultural knowledge, skills, and awareness. With a small sample size of eight graduate counselor-trainees in CACREP-accredited clinical mental health counseling and school counseling programs, Friedman tests and Wilcoxon signed-rank tests were employed to analyze the data. The results demonstrated statistically significant improvement on counselor trainees’ multicultural counseling competency, particularly their multicultural knowledge throughout the course, and particularly from immediately before the ICIE in Japan, after ICIE, and to the end of the multicultural counseling course. Limitations and implications based on the analysis results are also discussed.