Difficulty learning mathematics is generally caused by the nature of mathematics that has abstract objects. Based on interviews with homeroom teacher IV, it was conveyed that the causes of mathematics learning problems were (a) lack of student interest in learning, (b) students lack critical thinking (c) students lack focus on learning (d) abstract material. The success of the teaching and learning process can be measured from the selection of the learning model used. The success of the teaching and learning process can be measured from the selection of the learning model used. The selection of this model aims to make students accept and understand the material provided. Researchers want to improve the learning process by conducting PTK with the title "Application of the Cooperative Learning Model of the Numbered Heads Togeteter (NHT) Type to Improve Student Learning Outcomes in Mathematics Subjects". This research is a class action research (PTK). Learning outcomes in Mathematics subjects after implementing the Numbered Heads Togeteter (NHT) model in the first cycle obtained complete data as many as 12 students with a percentage of 60% and those who have not completed 8 students with a percentage of 40%, then still have not reached the predetermined target of 80%. In the second cycle, there was an increase from the previous cycle, 17 students completed with a percentage of 85% and those who had not completed as many as 3 students with a percentage of 15%. Then the learning results have reached the predetermined target.