The background of this research is the students low critical thinking skills and cooperative attitude of fourth grade of SD Negeri 3 Karangnanas. This study aimed to improve the students critical thinking skills and cooperative attitude on Theme 8 Daerah Tempat Tinggalku through the learning Problem Based Learning model for Grade IV of SDN 3 Karangnanas. This is a classroom action research with two cycles. The subjects of this study were grade IV students. The instruments used were tests and nontests. Data were collected using evaluation questions and questionnaires to find out the improvement in students' critical thinking skills and cooperative attitudes. The results of this study indicate that critical thinking skills obtained an average score of 3.0 with quite good criteria in cycle I and it increased to 3.6 with good criteria in the second cycle. An increase also occurred in the attitude of students cooperation taken from questionnaire sheets in each cycle. The results obtained from the questionnaire showed that the attitude of student cooperation obtained an average score of 3.20 with good criteria in cycle I, then it increased to 3.63 with very good criteria in cycle II. The results showed that the application of the Problem Based Learning model could improve the students and the students cooperation attitude.