The object of this study was to show how prospective elementary mathematics teachers define and classify the quadrilaterals and to find out their images. This research was a qualitative study. It was conducted with 36 prospective elementary mathematics teachers studying at 3rd and 4th years in an educational faculty. The data were collected by semi-structured interview. The collected data were analyzed by inductive content analysis. It was determined that prospective teachers made personal definitions for quadrilaterals and based on these definitions it was seen that there were inaccuracies in their perceptions. Some prospective teachers' images in rhombus caused problem on indicating the differences between rhombus and square. It was revealed that the prospective teachers drew defectively, especially rhombus and trapezoid figures. Furthermore, the prospective teachers did not prefer inclusion relations for the classifying quadrilaterals and made partition classifications, in general.