This study aims to determine the application of the cooperative learning model of group investigations to improve social studies learning achievement of students in class IX.E SMP Negeri 12 Mataram odd semester 2012/2013 academic year. This study was designed using Classroom Action Research. The subjects of this study were 34 students of class IX-E SMP Negeri 12 Mataram, consisting of 15 female students and 19 male students. The choice of class IX-E from 6 classes in SMP Negeri 12 Mataram was because social studies was a subject for which class XI-E students had a low level of mastery compared to other classes. While the research procedure through stages, namely planning, action, observation, and reflection. The results showed that the social studies learning outcomes of class XI.E students of SMP Negeri 12 Mataram in the 2012/2013 academic year, with the application of the Cooperative Investigation group model, namely the data on student learning outcomes in social studies learning has increased from the initial data obtained by 50.00%, increasing to 64.71% in the first cycle, to 73.53% in the second cycle and 88.24% in the third cycle. So student learning outcomes in social studies learning carried out by the teacher are very good. Learning planning, there is an increase from 65.00% in cycle I to 75.00% in cycle II and increase to 85.00% in cycle III. So the lesson planning carried out by the teacher is very good. While the implementation of learning carried out by the teacher also experienced an increase from 70.84% ​​in cycle I to 79.517% in cycle II and to 87.50% in cycle III. So the implementation of learning carried out by the teacher is also very good. Student learning activities increased in the first cycle by 64.84%, to 75.00% in the second cycle and 82.14% in the third cycle.