Professional vision research lacks behind regarding the investigation of attention processes in teaching action. In this study, eye movements of preservice teachers were assessed by mobile eye-tracking technology (MET). Eye movements of N = 7 preservice teachers while teaching in standardized instructional situations (M-Teach) and while teaching in classroom were recorded and analyzed with regard to fixation frequency and fixation duration. According to assumptions of expertise research, the results show that preservice teachers strongly differ in their focus of attention. Furthermore, they show that preservice teachers distribute their attention only over a few pupils while teaching. The findings provide important implications with regard to the question how to support attentional processes even at an early stage of professional development, for example by observing own MET videos.