This study was aimed to improve students' mathematical communication skills through the cooperative learning model of Number Heads Together (NHT). This is classroom action research consisted of 2 cycles. Each cycle consists of 2 meetings consisting of 105 minutes. The procedure for implementing each cycle includes planning, actions, observation, and reflection. The CAR design by Kemmis and Mc. hashtags were used in the design of this study. The subjects of this study were the fifth-grade students of SD Negeri 2 Cindaga with a total of 37 students. Test and non-test techniques were used as the data collection technique. Qualitative and quantitative analysis were used in the data analysis. Results of the research showed that there was an improvement in students' mathematical communication skills as it was proven from the assessment using tests. The test involving evaluation and indicators of students' mathematical abilities have increased from 69.3% in the first cycle to 81.075% in the second cycle. It can be said that NHT cooperative learning can improve the mathematical communication skills of the fifth-grade students of SD Negeri 2 Cindaga.