The aim of this study is to examine the effect of argumentation over current teaching approach on scientific epistemological beliefs and 21st century skills of seventh grade students. This is a quasi-experimental design with pre-test and post-test control group. The sample of the study was composed of 79 seventh grade students (38 experimental; 41 control group) from two intact classes of an urban middle school instructed with the same teacher. The teaching methods were randomly assigned to the classes. The experimental group treated with argumentation, the control group treated with the current teaching approach without argumentation. As data collection tools; Scientific Epistemological Beliefs Scale and 21st century skills scale were used. Multivariance Analysis of Variance (MANOVA) was used for data analysis. The results showed that argumentation and the current teaching approach had a similar effect on students' scientific epistemological beliefs and 21st century skills.