This study examined the relationship between the use of vocabulary learning strategies and self-efficacy in medical English learning, and whether after an initial six-week course to master the basics of medical terminology, those with higher use of vocabulary learning strategies and those with a higher degree of self-efficacy would have significant score improvements in the medical English proficiency. Second-year medical students (N = 115; M age = 19.6, SD = 0.5; 82 men, 33 women) participated in the study. A one-group pretest-posttest design was used. Measures included medical English tests, the English Vocabulary Learning Strategies Survey (EVLSS), and the English Learning Self-Efficacy Scale (ELSES). Results showed that there was no significant correlation between vocabulary learning strategies and English learning self-efficacy. In addition, as a whole, vocabulary learning strategies and self-efficacy significantly predicted students’ score improvements in medical English proficiency.