Berdasarkan hasil observasi peneliti, siswa kelas VIII-B di salah satu SMP Kristen Kupang, belum mampu menunjukkan kemampuan kerja sama dalam pelajaran Matematika. Untuk mengatasi hal tersebut, peneliti menerapkan Team Quiz untuk membantu siswa mengembangkan kemampuan kerja sama. Selain itu, peneliti juga ingin mengetahui cara penerapan metode Team Quiz dalam meningkatkan kemampuan kerja sama antar siswa kelas VIII-B. Metode penelitian yang digunakan adalah Penelitian Tindakan Kelas (PTK) model Kemmis dan Mc Taggart. PTK ini berlangsung dalam dua siklus pada tanggal 5 Oktober 2015 hingga 9 November 2015. Instrumen yang digunakan adalah lembar observasi check-list mentor dan teman sejawat, lembar observasi rating scale mentor dan teman sejawat, lembar angket siswa, dan lembar wawancara mentor. Hasil Penelitian Tindakan Kelas (PTK) menunjukkan bahwa Team Quiz berdampak pada peningkatan kemampuan kerja sama antar siswa kelas VIII-B pada mata pelajaran Matematika. Jadi dapat disimpulkan bahwa penerapan Team Quiz dapat meningkatkan kemampuan kerja sama antar siswa kelas VIII-B pada mata pelajaran Matematika. / The fact was students grade VIII in a school in Kupang, did not show their teamwork capability. To overcome this problem, the researcher implemented Team Quiz to help the students in improving their teamwork capability. Moreover, researcher wanted to know how the Team Quiz was implemented in order to improve teamwork capability of students grade VIII. This research method which was used in this Classroom Action Research (CAR) was Kemmis and Mc Taggart model. This CAR was conducted into two cycles on October 5th 2015 until November 9th 2015. The researcher used check-list observation sheet, rating scale observation sheet, students‟ questionnaire form, and mentor‟s interview sheet. The result of this CAR showed that Team Quiz could improve students‟ teamwork capability. Thus, it could be concluded that the implementation of Team Quiz was successful to improve students‟ teamwork capability.