This study was motivated by the prevalence of juvenile delinquency, which indicates that moral education in schools has not been entirely successful in internalizing moral values in a profound and practical manner. In addition, the moral content in Islamic Religious Education (PAI) textbooks is considered to be unfocused and incomplete. This study aims to develop a supplement book on morals based on the interpretation of the Qur'an as teaching material to support PAI at the Senior High School (SMA) level, as well as to test the feasibility and user response to the developed book. The method used is Research and Development (R&D) with the ADDIE model, which includes the stages of analysis, design, development, implementation, and evaluation. The research instruments consisted of a needs analysis questionnaire, expert validation sheets, and teacher and student response questionnaires. The results showed that the supplementary book received positive responses from 88.2% of teachers and 96.2% of students, while the expert validation results showed an average score of 3.58 out of 4.00 (92%) with a category of very feasible. This supplementary book consists of three volumes containing morals towards Allah and oneself, morals towards fellow human beings, and despicable morals, supplemented with verses from the Qur'an, interpretations, practical examples, and reflective exercises. Thus, this book is suitable for use as a supplement to PAI learning to strengthen the moral education of high school students. Abstrak Penelitian ini dilatarbelakangi oleh masih maraknya kenakalan remaja yang menunjukkan bahwa pembelajaran akhlak di sekolah belum sepenuhnya berhasil menginternalisasi nilai-nilai moral secara mendalam dan aplikatif. Selain itu, materi akhlak dalam buku Pendidikan Agama Islam (PAI) yang beredar dinilai belum fokus dan komprehensif. Penelitian ini bertujuan untuk mengembangkan buku suplemen akhlak berbasis tafsir Al-Qur’an sebagai bahan ajar pendukung PAI di jenjang Sekolah Menengah Atas (SMA), serta menguji kelayakan dan respons pengguna terhadap buku yang dikembangkan. Metode yang digunakan adalah Research and Development (R&D) dengan model ADDIE yang meliputi tahap analisis, desain, pengembangan, implementasi, dan evaluasi. Instrumen penelitian berupa angket analisis kebutuhan, lembar validasi ahli, serta kuesioner tanggapan guru dan siswa. Hasil penelitian menunjukkan bahwa buku suplemen memperoleh respons positif dari guru sebesar 88,2% dan siswa sebesar 96,2%, sedangkan hasil validasi ahli menunjukkan skor rata-rata 3,58 dari 4,00 (92%) dengan kategori sangat layak. Buku suplemen ini terdiri atas tiga jilid yang memuat akhlak terhadap Allah dan diri sendiri, akhlak terhadap sesama manusia, serta akhlak tercela, dilengkapi ayat Al-Qur’an, tafsir, contoh aplikatif, dan latihan reflektif. Dengan demikian, buku ini layak digunakan sebagai penunjang pembelajaran PAI untuk memperkuat pendidikan akhlak siswa SMA.