This study was conducted to investigate the students’ attitude on using English and Indonesian language as medium of instruction in English language classroom. It was aimed to find out students’ attitude towards the use of English and Indonesian and the factors contributed on it. This research employed mixed method in which the researcher used the questionnaire and interview to collect the data. The participants consisted of English Education Department Students in the academic year 2017; twenty three (N=23) students participated in the questionnaire and six (N=6) students purposively selected to participate in the interview. The findings of the research revealed that students had positive attitude on using English and Indonesian language as medium of instruction. They agreed to use English as the main medium of instruction in English language classroom, and Indonesian language was only used when needed to express their aspirations and to get explanation of the learning topics clearer. There were several factors that contribute in shaping students’ attitude on using language, which are: (1) self-confidence, (2) interest, (3) prestige, and (4) identity implication is discussed.