The background of this research was the low critical thinking skills and environmental attitudes of students. This study aimed to improve students' critical thinking skills and environmental care attitude by using the Children Learning in Science (CLIS) model. This was a Classroom Action Research (CAR). The research consisted of two cycles, each cycle consisted of two meetings containing planning, action, observation and reflection. The subjects of this research were 36 students of Grade V consisting of 10 male students and 26 female students. Data collection instruments used students' critical thinking skills tests, environmental care attitude questionnaires, environmental care attitude observation sheets, teacher activity observation sheets, and student activity observation sheets. The results of improvement could be found in each cycle. In cycle I, the percentage of completeness of critical thinking skills test was 26.40% and it increased to 79.25% in cycle II. Students' critical thinking skills improved in each cycle. In the meeting 1 of Cycle I it obtained a percentage of students completeness of critical thinking skills showed 16.7%, at meeting 2 it obtained a percentage of 36.1%. In the meeting 1 of Cycle II, the percentage of critical thinking skills of 75% was obtained while in meeting 2 a percentage of 83.3%. was obtained. Students environmental care also increased in cycle I and cycle II. Cycle I obtained an average of 2.35 and increased to 3.04 in the second cycle. The results of this study indicated that the use of the Children Learning in Science (CLIS) model was able to improve students critical thinking skills and environmental care attitudes of grade V in SD Negeri 1 Pejogol.