Practical courses are very important in teachers' professional training. It is important that teachers learn professional knowledge and skills by personal experience, and it can increase the quality of their teaching. The accuracy of the practice should be considered for the practical studies of pre-service teachers. When the practices do not include feedback, the connection between theoretical information and practice is not successfully established, which leads to performances to be taught adequately, but in fact insufficiently. The aim of this study is to determine pre-service science teachers' opinions about the use of feedback during the preparation of teaching materials. This is a case study, a qualitative research method. The study data were collected using an opinion form which included open-ended questions as well as interview questions. Pre-service teachers' written explanations to the open-ended questions were analyzed using content analysis, a qualitative analysis method. In addition, the study used descriptive analysis to assess the data that were collected during interviews with the purpose of obtaining further information. The research results show that a majority of teachers had positive opinions about feedback. They stated that feedback helped them to recognize and correct their mistakes and deficiencies, enabled meaningful and permanent learning, contributed to in-class communication and could be useful in all stages of formal education.