A language of instruction is used to deliver explanations about the concepts that are taught, discuss among students and teachers, and solve academic tasks such as exercises and assignments. At the Islamic University of Technology (IUT), students are drawn from different OIC countries whose language background is either the host country's language, e.g. Bangla, or other OIC member state languages e.g. French, Arabic, or English. This study investigates the implications of students’ language background towards their academic performance in IUT with specific objectives of assessing the impact of student’s level of English Language (EL) proficiency against their academic performance and determining the relationship between the constructs of the level of English Language proficiency and academic performance. The quantitative research design was used including close-ended questionnaires to collect data about the implication of language background on students’ performance. It was discovered that the implication of writing on students’ performance was minor and depended on the insight it was viewed in. Secondly, reading played an important part in building students’ confidence, increases participation and self-expression. Third, it was noted that perceived understanding had a slightly negative impact on student performance and, finally reading as part of background language had a significant positive role in the performance of students. Other factors such as the background of students in terms of origin, students’ interest in courses, etc. also influenced students’ academic performance. Further study in the future could explore other factors that determine students’ performance and issues of language to improve engineering knowledge and skills.