Penelitian ini dilaksanakan berdasarkan hasil pengamatan selama beberapa pertemuan di kelas XI IPA 2, yaitu kurangnya keaktifan belajar siswa dalam kelas. Keaktifan belajar siswa penting dalam pembelajaran karena mempengaruhi perkembangan siswa dan keberhasilan pembelajaran dalam kelas. Oleh karena itu, peneliti memutuskan untuk menerapkan metode pembelajaran kooperatif tipe Jigsaw untuk meningkatkan keaktifan belajar siswa di kelas XI IPA 2 di salah satu SMA Kristen di Cikarang dan untuk mengetahui cara penerapannya. Metode penelitian yang digunakan ialah Penelitian Tindakan Kelas (PTK) menurut Pelton, dilaksanakan sebanyak dua kali penerapan yang melibatkan 21 orang siswa. Instrumen untuk memperoleh data penelitian yang digunakan yaitu RPP, lembar umpan balik, jurnal refleksi peneliti, lembar observasi, wawancara dan angket siswa. Berdasarkan hasil analisis data dari instrumen yang digunakan seluruhnya menunjukkan bahwa penerapan metode pembelajaran kooperatif tipe Jigsaw dapat meningkatkan keaktifan belajar siswa kelas XI IPA 2 di salah satu SMA Kristen di Cikarang dengan 9 (sembilan) langkah penerapan dengan rata-rata persentase keaktifan belajar siswa 80% pada pertemuan pertama dan 83% pada pertemuan kedua./ This research was carried out based on the results of observations during several meetings in class XI IPA 2, namely the lack of active learning of students in the class. Student learning activeness is important in learning because it affects student development and the success of learning in the classroom. Therefore, the researchers decided to apply the Jigsaw cooperative learning method to increase the learning activeness of students in grade XI IPA 2 as one of the Christian High Schools at Cikarang and to find out how to apply it. The research method used was Classroom Action Research (CAR) based on Pelton model, implemented twice that involved 21 students. The instruments that used to obtain research data were RPP, feedback sheet, researcher reflection journal, observation sheet, interview and student questionnaire. Based on the results of the analysis of the data from the instruments used entirely, it shows that the implementation of the Jigsaw type cooperative learning method can increase the learning activeness of XI IPA 2 students as one Christian High School at Cikarang with 9 (nine) implementation steps with average percentage of 80% student learning activeness at the first meeting and 83% at the second meeting.