The purpose of this study was to: (1) to determine the effect of problem-based learning (PBL) model on critical thinking skill, and (2) to determine the effect of PBL model on environmental attitude. This study used a quasi-experiment model with a pretest-posttest control group design. The subjects of this study were students of Social Sciences Education Program, Universitas Islam Negeri Maulana Malik Ibrahim Malang, Indonesia, academic year 2018/2019. The sampling technique used purposive sampling and determined 25 subjects in each experimental and control class. Data collection used a test as an instrument of critical thinking skill and a questionnaire that were used to know the students' environmental attitude. The data analysis used independent sample t-test. The results showed: 1) there is a significant influence of PBL model on students' critical thinking skill (p=0.010) and 2) there is a significant influence of PBL model on students' environmental attitude (p=0.000). The PBL model has higher influence on critical thinking skill and environmental attitude than to conventional model. The use of problem-based learning models in activities to solve environmental problems encourages students' critical thinking skills to foster an environmental attitude.