This academic essay is an assessed coursework in Approaches and Methods in Language Teaching for taught postgraduate in School of Languages, Linguistics, Queen Mary University of London. This essay seeks to identify the necessity of inclusion of First Language in foreign language teaching and its following positive and negative impacts. Involving Target Language in language lessons is a bright idea due to its cognitive, communicative and social functions, though it might cause a few problems, such as the limited effect on elite students, the inefficient and time- consuming learning process, student’s over-reliance of L1. In the end, the essay provides a few teaching suggestions for language teachers.