Problem Statement: One of the main aims of constructivism is to improve critical thinking skills/tendencies via experiences. In this sense, it is believed that the more the constructivist-learning environment is improved, the more the appropriateness of supporting critical thinking is improved. However, no study has yet statistically tested this belief. Purpose of the Study: The aim of this study is to determine the regression level of constructivist learning environment characteristics on classroom environment characteristics supporting critical thinking according to the teachers participating in the study. Method: The study is a regression study at relational screening model. The sample of the study consists of 351 teachers working at primary and secondary schools in Kutahya city center and surrounding villages. The Constructivist Learning Environments Questionnaire and Critical Thinking Supportive Teachers' Behaviors Inventory were used as data collection tools. During the data analysis, the Pearson correlation test was conducted to determine the relation between the two variables. To determine the regression level of constructivist learning environment characteristics on classroom environment characteristics supporting critical thinking, multiple regression analysis was conducted. Findings and Results: The results of the regression analysis revealed that constructivist learning environment characteristics explain the 44% of the total variance of classroom environment characteristics supporting Open Mindedness; 50% of the total variance of classroom environment characteristics supporting High-Level Questioning; 40% of the total variance of classroom environment characteristics supporting Questioning of the Accuracy and Reliability of Information; 47% of the total variance of classroom environment characteristics supporting Seeking Causes and Evidence; 48% of the total variance of classroom environment characteristics supporting Openness. Conclusion and Recommendations: In general, a medium-level, positive and significant relation was found between the sub-dimensions of the Constructivist Learning Environments Questionnaire and the sub-dimensions of the Critical Thinking Supportive Teachers' Behaviors Inventory. Furthermore, it was found that the constructivist learning environment characteristics could explain nearly half of the total variance in classroom environment characteristics supporting critical thinking. These results show that the belief expressed in the existing literature that aligning the classroom environment with constructivist learning environment characteristics is also effective in supporting critical thinking is true to a great extent.