The purpose of this study was to determine the views of pre-service Mathematics teachers' (PMTs) about GeoGebra and its use after being exposed to GeoGebra activities designing processes. This is a case study which was conducted with 36 PMTs. Three open-ended questions were used, after the completion of the 14-week process of GeoGebra training and designing of GeoGebra activities. The content analysis of the open-ended questions indicated that all of the PMTs think that GeoGebra has positive effects on their professional development. They also stressed that GeoGebra can contribute to students' academic achievement. In addition all the PMTs stated that they would like to use GeoGebra in their professional career. However, while more than half of the teachers stated that their use of GeoGebra in their professional lives depends on some conditions and the rest of them stated that they would use GeoGebra and expressed their reasons for using it.