The aim of this study was to investigate the effectiveness of GeoGebra software in preservice mathematics teachers' process of correcting and making sense of errors regarding the concept of the asymptote. Case study method, one of the qualitative approaches, was adopted in the study. The study group consisted of 11 preservice teachers studying in the mathematics teaching program. This study comprised of three parts: pre-GeoGebra application, during the GeoGebra application and after the GeoGebra application. Data were analyzed using descriptive analysis method. The participants' written answers before and after the GeoGebra-assisted application revealed that their approaches to possible errors regarding the concept of asymptote changed positively. Moreover, interviews with three participants who showed "development" "a partial development" and "no development " supported this result.