Research on English Medium Instruction (EMI) is rapidly increasing and well-documented worldwide; however, recent studies in EMI have given less emphasis on assessments in EMI classrooms. Indeed, assessment plays a significant role in informing teaching and learning competencies, but what to assess and how to assess are questions which have been neglected in EMI research. The controversy continues over whether it is necessary to assess language in content learning. This systematic review explores assessment practices in EMI centering on objectives, roles, and tools of assessment. The PRISMA flow diagram screening process was employed in the study selection to enhance the transparency and scientific validity of this review. Consequently, we identified assessment implementation for different purposes and highlighted critical findings based on an in-depth analysis of 13 studies on EMI assessments in different contexts. Findings revealed that assessments of English proficiency and content comprehension are widely found in formative and summative assessments. Although teaching English was not a primary goal of EMI, assessments of English skills were practiced in many contexts. This study provided a greater understanding of a holistic picture of EMI assessments that can benefit related stakeholders in selecting appropriate assessments for specific purposes in EMI classrooms. Moreover, this study called for further research on the empirical evidence of EMI assessments in diverse educational settings.