Medical learners’ achievement emotions during educational activities have remained unexamined in Asian cultural contexts. The Medical Emotion Scale (MES) was previously developed to assess achievement emotions experienced by North American medical learners during learning activities. The goal of this study was to create and validate a Japanese version of the Medical Emotion Scale (J-MES). We translated the MES into Japanese and conducted two initial validation studies of the J-MES. In the first pilot study, we asked five, native-Japanese, second-year medical students to assess their emotions with the J-MES during a computer-based clinical reasoning activity. Each participant was then interviewed to assess the clarity and suitability of the items. In a second, larger study, 41 Japanese medical students were recruited to assess the psychometric properties of the J-MES. We also conducted individual, semi-structured interviews with ten of these participants to explore potential cultural features in the achievement emotions of Japanese students. The first pilot study demonstrated that the J-MES descriptions were clear, and that the scale captured an appropriate range of emotions. The second study revealed that the J-MES scale’s profiles and internal structure were largely consistent with control-value theory. The achievement emotions of pride, compassion, and surprise in the J-MES were found to be susceptible to cultural differences between North American and Japanese contexts. Our findings clearly demonstrated the scoring capacity, generalizability, and extrapolability of the J-MES.