The purpose of this study was to determine the differences between preservice teachers' 21st century techno-pedagogical content knowledge (TPACK-21). The study group included 254 preservice teachers from the departments of Science Teaching and Mathematics Teaching at a state university in Turkey. In order to determine the preservice teachers' strong and weak points in terms of TPACK-21 and to reveal the differences between them in terms of their gender, computer use efficacies and Internet use frequencies, the clustering analysis method was used. For the purpose of confirming the evident difference between the TPACK-21 variables, one-way ANOVA was applied, and the effect sizes were determined (n2). It was found that for all the variables, there were significant differences between the clusters. Also, Bonferroni post hoc analysis conducted for the confirmation of the clusters revealed significant differences between the clusters for each factor influential on the students' TPACK-21 perceptions.