This study consisted of two stages. In stage A, 38 students were divided randomly into an experimental and a control group. The experimental group received lectures assisted by dynamic geometry software (DGS) and the control group received lectures using chalk and blackboard. The effects of DGS on metacognition and its components were quantitatively assessed. In stage B, follow-up interviews were carried out to understand the mechanism by which DGS improves metacognition. The results reveal that metacognition, especially for prediction and planning, can be significantly improved by using GeoGebra instead of the traditional lecture format. The findings suggest that visualization, dragging, dynamic platforms and immediate feedback are the four main factors underlying such developments.