The aim of this study is to examine the effect of block-based coding education on middle school students' computational thinking skills and attitudes towards coding with Blocky example. The training phase of the implementation process was planned and implemented by subject experts in 4 weeks and 2 hours a week. In the research, both quantitative and qualitative research methods and exploratory sequential design were used as mixed methods. In this study, quantitative research method and pretest- post-test control group semi-experimental pattern model was used as the research model. The universe of the study consists of 5th grade students studying at a secondary school in Aksaray province Eskil district of Türkiye in the 2019-2020 academic year. Within the scope of the research, the research participant group was determined considering that 5th grade students will receive coding training for the first time. In addition to the total number of students to be reached is 38, including 19 control and 19 experimental groups. While the "blocky" application used in block-based coding education was determined as the independent variable in the research, the students' computational thinking skills and their attitudes towards learning to code were determined as dependent variables. As a result of the applications and analysis, the difference between the values of students' computational thinking skills self-efficacy and attitudes towards learning coding before and after education is statistically significant. In order to determine the effect size of the Blocky block-based coding environment on the Information Computational Thinking Skills Self-Efficacy Scale (CTSES) and the Attitudes Toward Learning Coding Scale (ATLCS), the eta squared value was examined. It can be said that the Blocky block-based coding environment has a "large" effect size on computational thinking skills, self-efficacy perception and on the attitude towards learning coding.