The design and development processes of instructional materials might be considered simple and clear because the pre-established instructional goals can lead the way. However, in practice, there are lots of issues to be considered during these processes. The quality of the material, appropriate visual design, usability, and acceptable amount of cognitive load are some of these issues. On the other hand, an instructional material needs to be as original as possible. In this study, we focused on the creativity of the instructional materials designed and developed by second year students from the Computer Education and Instructional Technologies (CEIT) department. We divided students into two groups: (1) CEIT students designing and developing materials about Information Technology (IT); (2) CEIT students designing and developing materials about Math. The main aim of this study is to understand how CEIT students' instructional materials differ when they design and develop materials, which are out of their field of experience. In other words, we tried to compare how the creativity of materials change when students create materials with familiar domain (IT) in comparison to unfamiliar domain (Math). Students worked on ten instructional materials such as digital story, animation, and worksheet for 14 weeks. The materials of students were evaluated in terms of creativity, and then they were interviewed. The students worked in groups of 4-5, and during the material development period, we as researchers observed and took notes about the whole process. The findings indicated that materials developed in familiar domain were higher in creativity than those of the unfamiliar. Students' explanations of creativity and their evaluations about the process helped us to understand the reasons of the produced materials' creativeness. Technical skills, authentic contributions, material type, and the boundaries of the content or familiarity were found as the primary factors affecting the design and development of creative instructional materials.