The establishment of an English Medium Instruction (EMI) program in any educational level including the university context becomes a controversial issue regarding whether the program should be kept running or not. The present study was conducted to investigate students' voices of EMI based on their different exposure period to English. To obtain the data, a mixed-methods approach was employed. A five-point Likert-scale questionnaire and semi-structured interview were administered to two groups of students who had experienced degrees of experience in EMI classes at a state university in Indonesia. There were 27 items in the questionnaire and six questions in the interview guide related to the importance of learning English, the future use of English, the ability to speak English, the importance of joining EMI classes, the teaching and learning process in all the categories, and there was no significant difference in the perceptions of the two groups. They agreed that having the ability to communicate in English was crucial. They were aware of the importance of English for their future lives and jobs. They stated that joining EMI classrooms was necessary and gave more chances for advancing learning. Furthermore, they reported a good atmosphere of learning in the EMI classes since the EMI teachers help them solve problems. Their friends were also helpful when they had difficulties with the EMI materials. The study results suggested that EMI was an effective program to improve students' English proficiency as well as their academic achievement.