Background and purpose: With the increase in the number of international medical students, there is an urgent need to develop programs to foster communication skills in Japanese, but the communication problems of international medical students are not clear. Methods: Semi-structured interviews and questionnaires were conducted with 10 international students to identify communication difficulties during clinical practice. Results: Regarding communication with patients, the frequently reported difficulties were difficulty in hearing elderly voices, difficulty with dialects, and difficulty with onomatopoeia. As for communication with health care professionals, the top concerns were not being able to understand jargon and difficulty in speaking concisely using technical terms. Discussion: Language input is a major problem. In educational institutions, they need to listen to a variety of speakers, learn frequent onomatopoeia, and practice oral case reports.