<p>English proficiency and motivation are critical determinants of learning outcomes in English medium instruction (EMI) courses. This study investigates the impact of students' English proficiency and academic motivation on EMI learning outcomes in Taiwanese management courses. A total of 97 questionnaires were collected from six management courses and analyzed using SPSS and partial least squares structural path modeling software SmartPLS 4. The measurement model results indicated that as a multidimensional construct, academic motivation can predict EMI learning outcomes. Among the three core facets of academic motivation, extrinsic motivation emerged as the strongest positive predictor of EMI learning outcomes, whereas amotivation showed significant negative effects on shaping EMI learning outcomes. Additionally, English proficiency was found to predict both EMI learning outcomes and amotivation levels. Students with CEFR ≤ B1 English proficiency exhibited higher amotivation, lower course grades, and worse self-reported learning outcomes, including content comprehension, confidence in undertaking future EMI courses, advancement in professional competence, and enhanced international mobility, than their ≥ B2 peers. Similar disparities in English proficiency, academic motivation, and learning outcomes were observed between domestic and international students. As a pedagogical implication, targeted support for domestic and less proficient students is recommended to mitigate these disparities.&#xa0;</p>