The purpose of this study is to examine the conceptual knowledge of mathematics teacher candidates about the sequence concept. This research is a case study in which qualitative methods are adopted. The first phase of the study was conducted with a total of 45 teacher candidates taking the course of Analysis III. In this stage, the "Sequence Knowledge Test" consisting of four open-ended questions developed by the researchers was used as a data collection tool to examine the concepts of the teacher candidates about the sequence concept. In the second stage of the research, individual interviews were made with 8 teacher candidates selected from the sample in order to conduct an indepth study on conceptual knowledge about the subject of the sequence. Content analysis was used to analyze the obtained data. As a result of the analysis of the data, important shortcomings were found in the concept knowledge of the teacher candidates.