This study involves a small-scale investigation of codeswitching in university classrooms. The perceptions of the use and the effectiveness of codeswitching were investigated from the perspectives of 23 instructors and 765 students in various fields at a Korean university. In addition, the actual use of codeswitching in the classroom by an instructor, teaching the theories of English education, was investigated. These two data sources have served as the subsequent main study. The results show that both instructors and students perceive the use of codeswitching is effective in learning English skills overall, but the instructors consider it more effective in reading while students perceive it more effective in listening. This study also explored the functions of codeswitching in the classroom. The findings suggest that the codeswitching is employed to accommodate the participants’ language preference or competence.