AbstrakPenelitian ini bertujuan untuk meningkatkan aktivitas dan hasil belajar siswa melalui model kooperatif think talk write berbantuan media leaflet pada materi perubahan lingkungan kelas X MIA 3 SMA Muhammadiyah 1 Pontianak. Metode penelitian yang digunakan adalah penelitian tindakan kelas yang dilakukan dalam dua siklus dengan dua kali pertemuan. Setiap siklusnya terdiri dari 4 tahapan yaitu: perencanaan, pelaksanaan, observasi, dan refleksi. Instrumen yang digunakan berupa lembar observasi aktivitas belajar siswa, lembar observasi proses pelaksanaan pembelajaran, dan tes hasil belajar. Hasil penelitian menunjukkan jumlah siswa dengan kategori aktif pada siklus I sebesar 60,61% dan meningkat pada siklus II sebesar 75,76%. Persentase ketuntasan hasil belajar siswa pada siklus I sebesar 75,76% dan meningkat pada siklus II sebesar 87,88%. Persentase proses pembelajaran siklus I sebesar 94.44% dengan kategori baik dan meningkat pada siklus II sebesar 100% dengan kategori baik. Secara keseluruhan pembelajaran kooperatif think talk write berbantuan leaflet  dapat meningkatkan aktivitas dan hasil belajar siswa pada materi perubahan lingkungan di kelas X MIA 3 SMA Muhammadiyah 1 Pontianak. AbstractThis research was aimed to improve students’ activities and learning outcomes through the ‘think talk write’ cooperative model using leaflet media in the material of environmental changes at Class X MIA of SMA Muhammadiyah 1 Pontianak. The method implemented in this research was classroom action research conducted in two cycles with two meetings. Each cycle comprised of four steps: planning, implementing, observation, and reflection. The instruments used in data collection were observation sheet of students’ activity, an observation sheet of the learning process, and a test. The findings showed that in cycle I, 60.61% of students were categorized active and increased in cycle II by 75.76%. The percentage of completeness of student learning outcomes in the cycle I was 75.76% and increased in cycle II by 87.88%. The percentage of the learning process in the first cycle was 94.44% in the good category and increased in the second cycle by 100% in the good category. Based on the findings, it was concluded that the selected learning model improved students’ activities and learning outcomes in the material of environmental changes at class X MIA 3 of SMA Muhammadiyah 1 Pontianak.