The use of first language in teaching and learning process is often found in English classes. In Indonesia, Bahasa Indonesia is also employed in many English classes. This might bring both advantages and disadvantages for the students. This study aimed to find out the students’ perception on the advantages and disadvantages of using Bahasa Indonesia in English classroom. The researcher used a qualitative approach and the research design was descriptive qualitative. The participants were two female and one male students of a private university in Yogyakarta. The researcher used interview as a method to gather the data. The findings revealed that the advantages of using Bahasa Indonesia were that the use of Bahasa Indonesia helped the students in speaking and in understanding the teacher’s explanation and instruction. The students also perceived that Bahasa Indonesia can be used to address the students’ different ability in English and helped the students in comprehending vocabulary. Related to the disadvantages, the students perceived that the use of Bahasa Indonesia in English classes hamper the students’ speaking skill, the learning process become limited, the students tend to use Bahasa Indonesia, the students get less knowledge of vocabulary, the students’ opportunities for English exposure limited, and the students unable to feel English language.