Hasil belajar kognitif peserta didik merupakan salah satu hal penting bagi peserta didik, guru, dan orang tua untuk melihat dampak proses belajar dalam kelas. Berdasarkan pengamatan peneliti, masih banyak peserta didik yang memperoleh hasil belajar kognitif di bawah standar. Hal ini disebabkan karena kurangnya fokus peserta didik dan metode pembelajaran yang diterapkan. Untuk mengatasi masalah tersebut, peneliti menerapkan metode numbered heads together dengan tujuan untuk melihat ada tidaknya peningkatan hasil belajar kognitif peserta didik melalui penerapan metode numbered heads together dan bagaimana metode ini meningkatkan hasil belajar kognitif peserta didik. Metode penelitian yang digunakan adalah Penelitian Tindakan Kelas (PTK) model Kemmis Taggart & Nixon yang berlangsung selama tiga siklus. Penelitian ini dilaksanakan di kelas VIII Sekolah X Sentani, Papua mulai 13 Oktober 2015 hingga 10 November 2015. Instrumen penelitian yang digunakan berupa lembar tes tertulis, lembar angket, lembar check list, dan lembar panduan wawancara. Berdasarkan penelitian ini, dapat disimpulkan bahwa penerapan metode numbered heads together dapat meningkatkan hasil belajar kognitif peserta didik. Hal ini terlihat dari persentase jumlah peserta lulus KKM siklus pertama, kedua dan ketiga secara berturut-turut yaitu 43%, 71% dan 79%. Metode ini diterapkan dengan baik sesuai langkah-langkahnya yang terdiri dari penomoran, menanyakan, menyatukan kepala, dan menjawab. / The students’ cognitive outcomes is one of the important thing for students, teachers, and parents to know the impact of the learning process in the classroom. Based on the researcher’s observation, there were many students who have cognitive outcomes below the standard. It was happening because the lack of the students’ focus and the learning method that existed. To solve the problem, the researcher implemented the numbered heads together method in order to know whether there is an increase the students’ cognitive outcomes through the implementation of the numbered heads together method and how this method improve the students’ cognitive outcomes. The research method used is Class Action Research (CAR) modelled by Kemmis Taggart & Nixon with total three cycles. The research was conducted in grade VIII Sekolah X Sentani, Papua from October 13th 2015 to November 10th 2015. The research instruments used are written test sheet, questionaire sheet, check list sheet, and interview guide sheet. Acoording to this research, the researcher concluded that the implementation of numbered heads together method increases the students’ cognitive outcomes. It is proved from the percentage number of students who passed the standard from the first cycle, second cycle and third cycle; it showed the successfull increase from 43%, 71% to 79%. This method was implemented well based on the steps which consist of, numbering, questioning, heads together, and answering.