Humor is one of the teaching tools used by lecturers in the teaching process. Thus, this study was conducted to investigate the students’ perception on teachers’ humor in teaching and learning process including the effects of using humor and the extent of humor used by English Language Education Department (ELED) of a private university in Yogyakarta teachers in teaching and learning process. This study applied qualitative research design with four students of EED of UMY batch 2013 as the participants. In addition, interview was used as the data collection method. The results showed that the effects of humor are divided into positive and negative effects. The positive effects are namely students were relaxed in the learning process, students remembered and understood the material more easily, students felt closed to the lecturers, students were not afraid of being active in the classroom, and students became more enthusiastic to learn. The negative effects include students cannot stay focused and the time of study will be reduced. In addition, the students also give their perception and suggestion that humor has no negative effect when the lecturer did not use humor in negative meaning. Next, students’ perception toward the extent of humor used by ELED teachers in teaching learning process are when the students look bored, sleepy, when students were not focused anymore, when situation in the classroom getting crowded, when teacher teaching at afternoon classes, and when the durations of lesson is long.