ABSTRAK Hasil belajar siswa kelas XI MIA di SMA N 8 Pontianak pada mata pelajaran biologi masih rendah, khususnya materi sistem imun dengan presentase ketuntasan 30,17%. Selain itu, dalam proses pembelajaran media yang digunakan hanya berupa lembar kerja siswa (LKS) menyebabkan suasana belajar menjadi monoton dan kurang mengikutsertakan siswa dalam belajar. Penerapan media pembelajaran booklet dibutuhkan untuk menyalurkan pesan sehingga dapat membantu mengatasi masalah tersebut. Penelitian ini bertujuan untuk mengembangkan media pembelajaran booklet sistem imun. Metode yang digunakan dalam penelitian yaitu model pengembangan 4-D (four D model). Berdasarkan penelitian diperoleh hasil validasi media booklet yaitu sebesar 89,3% dengan kriteria sangat valid dan kepraktisan media sebesar 89,3% dengan kategori sangat praktis. Respon siswa terhadap media booklet ada uji skala kecil dan skala besar berturut-turut yaitu sebesar 90,2% dan 86,5% (kategori respon positif). Berdasarkan pengukuran efektifitas penggunaan media diperoleh nilai gain sebesar 0,51 dengan kategori sedang. Berdasarkan hasil penelitian dapat disimpulkan bahwa hasil pengembangan media booklet dapat dikatakan valid, praktis dan efektif.Kata kunci: Pengembangan Media Pembelajaran, Media Booklet, Hasil Belajar, Sistem ImunABSTRACT Students learning outcomes in eleventh grade of SMAN 8 Pontianak in biology subject, especially immune system was still low with the passing percentage 30,17%. Beside of that, the learning process used media only a students worksheet. It cause the learning not involving the student so situation became monotonous. Booklet as the learning media needed to overcome that  problem. This study aimed to develop booklet as a media to teach immune system. Method used in this study used four D model development. Based on the study conducted, the validations result was 89,3% categorized as very valid and the practicality was 89,3% categorized as very practical. Students responds toward the booklet in large and small scale each were 90,2% and 86,5% (positive respond). Based on the efectivity measurement on booklet, the value was 0,51 categorized as intermediate. Based on the results, can be concluded that developing booklet as media was valid, practical and effective.Keywords:Developing Learning Media, Booklet Media, Learning Outcomes, Immune System.