Purpose: This study will find out student misconceptions about geometrical figures, particularly polygons and quadrilaterals. Thus, it will offer insights into teaching these concepts. The objective of this study, the question of "What are the misconceptions of seventh grade students on polygons and quadrilaterals?" constitutes the problem sentence of the research. Research Methods: The study was conducted in five different schools in Gaziantep, and the data consist of 229 students who are in the seventh grade. In the quantitative part, descriptive statistics, t-tests and one-way ANOVA tests were applied by using SPSS 17.0 software. Findings: The results indicate that students display various misconceptions about polygons and special quadrilaterals. When the students were asked to draw squares, rectangles, trapezoids and equilateral quadrangles, almost all the participants drew prototype figures. It was discovered that, as the level of academic success increased, the risk of misconception decreased in return. Implications for Research and Practice: In the research, students displayed certain misconceptions when questions about the concept of diagonals were presented. Furthermore, in diagnostic test results, the outcome that the intermediate-level students had more misconceptions compared to low-level students might be because the low-level students left more questions blank. By means of conducting qualitative studies, it is possible to determine the thoughts that cause misconceptions. In the lesson content, permanent formula and prototype figures should be avoided. Instead, lessons should be imparted in the manner that reflects actuality and that expresses the core of the perceived subject.