An effective learning environment can be provided when teachers adopt metacognition-based teaching as a part of their course instructions. A well-developed metacognitive teaching approach can effectively develop students' problem-solving strategies. In addition to that contribution, it can provide opportunities for students to notice their own strengths and weaknesses together. Therefore, awareness of metacognitive processes should be passed on to students. The purpose of this study is to reveal what metacognitive strategies are adopted by preschool teachers while implementing mathematical activities, to examine their behaviours regarding these strategies, and to investigate how they structure the instruction. The research was constructed as a case study. The data were collected from 15 participating preschool teachers. A semi-structured observation form was used to collect the data. The data collection tool consisted of five dimensions and 24 sub-dimensions concerning aspects of metacognition. Mathematical activities of the participants were tracked by a researcher, and instructional behaviours of the participants were documented in accordance with items in the form. A descriptive analysis was carried out to examine the major characteristics of the dataset. The results indicated that preschool teachers demonstrate some metacognition-based behaviours. However, they do not adequately perform metacognitive skills. This evokes the idea that the teachers do not have adequate knowledge of metacognition. Hence, it is suggested that in-service training or some courses on metacognition-based teaching should be provided for teachers to increase their awareness.