The purpose of this study was to investigate the tessellation performance of 8th-grade students and factors affecting their performance. Student performances have been examined in two dimensions: identification and completion of tessellation. In this context, a diagnostic test containing two main questions with the content of determining whether the motifs are tessellations and completing the tessellations was prepared. The test was applied to 40 eighth grade students. The findings show that students exhibited good performances in determining whether a pattern is tessellation and their performances were close to each other according to tessellation types. It was found that students' completion performances of the tessellation varied according to the tessellation types. In addition, the factors affecting these performances were also revealed as a result of the study.