The training of individuals who produce science is based on the way they think. Critical thinking is one aspect of thinking. The study's purpose is to analyze the effect of integrating critical thinking based on 4MAT (CT-4MAT) instruction to develop students' critical thinking dispositions. A pre-test post-test quasi-experiment design was used. It surveyed 60 7th-grade students (30 experiment and 30 control) attending a middle school in a city center in the northwest of Turkey. In the experiment group, the science curriculum, including the CT-4MAT instruction, was used, and in the control group, the science curriculum, not including this strategy, was used. The data were collected using the "Critical Thinking Disposition Inventory" and the "Attitudes and Views about Biodiversity Loss Scale". The analysis results showed a significant difference in favor of the experiment group students in terms of the scores of critical thinking disposition. The analysis results showed a significant difference in favor of the experiment group students in terms of the scores of critical thinking disposition. The experiment group evaluated themselves as more part of nature in their responses and dealt with biodiversity, the basis of sustainable living in critically. The control group's responses showed individuals do not solve problems concerning biodiversity and do not seek solutions unless the problems are affecting them. This study shows that the CT- 4MAT instruction helped to promote students' Critical thinking dispositions.