Although augmented reality has become one of the most commonly used materials that support learning, especially in learning geometric concepts, it is avoided to be used in the lessons due to its complex structure. At that point, artificial intelligence working as a personal assistant in many fields can help us learn to produce our own model with augmented reality by coping with its complexity. In this study, it is aimed to examine both the effectiveness of Artificial Intelligence (AI) assisted Augmented Reality (AR) activities on the development of the preservice teachers' (PSTs) geometric reasoning and their practicality in use. To this end, an interactive learning environment with AI assisted AR activities including Chat Generative Pre-Trained Transformer (ChatGPT), Blender and MyWebAR, and lasting five weeks have been designed. The participants in this case study were 15 preservice mathematics teachers selected by maximum variation and criterion sampling techniques. The data were collected through AI assisted AR activities, two semi-structured interview forms, focus group interviews, anecdotes, activity forms and test. The analysis results have been reported under three groups about the PSTs' test results, experiences on AI assisted AR activities and thoughts about the activities. To conclude, it has been observed that the PSTs' conceptualization and geometric thinking levels have been improved. Moreover, their thoughts have been illustrated with the themes of "cognitive dimension", "affective dimension", "technological dimension" and "employability dimension".