Assessment is one of the most necessary elements in teaching and learning process. By assessment in internship program, the pre-service teachers can ensure students’ ability. Pre-service teachers are students in educational major who are teaching in the school. Internship program is one of the important aspects which the pre-service teachers need to do in order to obtain their degree and experience to become real teachers in the future. This research used descriptive qualitative in order to explore pre-service teachers’ perception about the importance of assessment and the challenges in designing assessment during teaching internship program for preservice teachers’. The data were gained by interviewing four experienced pre-service teachers’ in a private university in Yogyakarta. The result showed that there are three the importance of assessment, these importance included, helping to adjust the material and students’ ability, to see the ability of students, and improving pre-service teacher content knowledge. Additionally, there are two challenges in designing assessment during their teaching internship program for pre-service teacher, namely determining the length of assessment that suits the available time and determining the level of difficulty of assessment.