The purpose of this study is to investigate high school mathematics teachers' approaches to errors in the derivative of the implicit function. For this purpose, teachers' approaches to errors were examined in two parts: justifying the source of the error and demonstrating a teaching approach to eliminate the error. In the study, case study design, one of the qualitative research models, ise used. The participants of the study are 5 mathematics teachers working in general high schools affiliated with the National Education of Turkey (NET). The data collection tool of the study is error-based scenarios developed by the researchers. The data of the study is obtained through one-on-one interviews with teachers. While the data of the first part of the study is analyzed with the help of open coding, the data in the second part is examined with the help of descriptive analysis. Teachers' interventions towards student mistakes are explained with four approaches: "explaining-showing", "providing information", "making aware" and "understanding or moving the thought forward". The findings of the study reveal that teachers are not able to accurately determine the reason for the error in one of the three scenarios. In addition, the findings show that teachers are inadequate in producing appropriate strategies in the context of approaching errors.