The purpose of this study is to improve mathematics learning outcomes for studens in grades IV-B MI Muhammadiyah Godog by using the think pair share model. This research used the Classroom Action Research (CAR). The research was carried out in 3 cycles. This research design was conducted in class IV-B MI Muhammadiyah Godog with a total of 22 students. Data collection was done by documentation method. Data analysis used quantitative descriptive percentage techniques, namely learning completeness, average learning outcomes, and observation sheets. The results show that (1) the implementation of the think pair share model is done smoothly according to the lesson plan (LP) that has been prepared, which is 80,35%. (2) the application of the think pair share model can improve mathematics learning outcomes in the area of flat shapes from pre-cycle to cycle III. In the first cycle, there is an increase, namely the average value of 60,14 with the percentage of learning completeness 22,73% to 62,38 with percentage of learning completeness 40,91%. In the second cycle, the average value increase to 69,09 with the percentage of completeness learning 63,64%. In the third cycle the average value increase to 79,10 (a value above the KKM) with a percentage of learning completeness 81,82%. Based on this research, teachers need to apply and develop learning models well, so that student learning outcomes continue to increase.