This study uses a mixed research method to examine the effects of a five-week intercultural competence (ICC) training program on 9th-grade high school students. Analysis of paired-sample ttests revealed a significant increase in overall ICC levels, particularly in the knowledge and consciousness dimensions, indicating the training's effectiveness. However, despite the statistical significance of these results, the small effect sizes suggest that its impact is limited. Additionally, no significant changes were observed in the affective, behavioral, and self-efficacy dimensions, indicating that the training did not immediately alter attitudes or behaviors. On the other hand, interviews revealed that while students initially had limited cultural perspectives, mainly focusing on surface aspects and national stereotypes, the training broadened their views. Participants reported becoming more mindful of cultural differences and gaining new insights, such as understanding culture shock. There is a noticeable gap in ICC research related to high school students. The study highlights the importance of integrating ICC into English language learning to better prepare students for effective interaction in an increasingly globalized world.