This study dwells on the effect of native language on students’ academic performance in English language with a focus on North-Eastern Nigerian Federal Polytechnics. Namely, these include Federal Polytechnic, Bali, Kaltungo, Mubi, Damaturu and Bauchi precisely. The target participants of this study are students of National Diploma (ND) who have been taken English as general studies from some departments in the study area. Six departments are sampled using simple random sampling technique accordingly. The study intends to use a cross-sectional survey design and questionnaires as an instrument for data collection from the participants. A mixed method which involves both quantitative and qualitative are utilized for summary of data using descriptive statistics from the tables. On the other hand, qualitative data are put under the tables and follow with explanations. A judgement rule is drawn to decide significant findings and insignificant findings in the study. The Interlanguage Theory, proposed by Larry Selinker in 1972, is highly relevant to this study as it provides a framework for understanding how learners' native languages influence their second language acquisition, particularly in educational settings.  The results find out that the use of native language have some negative effects on academic performance of the students in English language in Federal Polytechnics, under study. Therefore, the findings showcase that native language affects the participants' academic performance such as writing and speaking in English as a language of instruction. In response to that, some useful recommendations such as the teaching methodology should be interactive in English for a classroom rapport. That will motivate the students to participate more and improve their performance in the target language. In essence, this corresponds to a claim makes by Krashen who posits that once the adequate input is made available in a L2 class, the grammar will come up automatically. So, the results are useful for English language teachers, students, curriculum developers, young scholars and interested person or organization