ABSTRACTThis study aims to determine the improvement of students' collaboration skills through the implementation of the STEM-based Project Based Learning (PjBL) model at Nurul Hasaniah Education Foundation Junior High School. This study uses a quantitative approach with a Pre-Experimental Design through a One Group Pretest-Posttest Design. The research sample consisted of 20 students of grade IX-2 Tahfiz selected using a purposive sampling technique. Collaboration skills data were obtained through peer assessment, self-assessment, and collaboration skills observation sheets conducted before and after the implementation of the STEM-based PjBL model. Collaboration skill indicators observed included active contribution, productive work, flexibility and compromise, responsibility, mutual respect, and effective communication. The results showed that students' collaboration skills increased after the implementation of the STEM-based PjBL model. Before the treatment, students' collaboration skills were still in the medium and low categories, indicated by low discussion participation, group work, responsibility, and communication between students. After the treatment, the assessment results showed an increase in all indicators with high and very high categories. Observations showed that the flexibility and compromise indicators achieved the highest percentage at 97.5%, while effective communication reached 80%. Thus, the implementation of the STEM-based Project-Based Learning model was effective in improving students' collaboration skills at the Nurul Hasaniah Education Foundation Middle School.Keywords: Collaboration Skills, Project Based Learning (PjBL), STEMABSTRAKPenelitian ini bertujuan untuk mengetahui peningkatan keterampilan kolaborasi siswa melalui penerapan model Project Based Learning (PjBL) berbasis STEM di SMP Yayasan Pendidikan Nurul Hasaniah. Penelitian ini menggunakan pendekatan kuantitatif dengan jenis penelitian Pre-Experimental Design melalui desain One Group Pretest-Posttest Design. Sampel penelitian berjumlah 20 siswa kelas IX-2 Tahfiz yang dipilih menggunakan teknik purposive sampling. Data keterampilan kolaborasi diperoleh melalui penilaian teman sejawat (peer assessment), penilaian diri (self-assessment), dan lembar observasi keterampilan kolaborasi yang dilakukan sebelum dan sesudah penerapan model PjBL berbasis STEM. Indikator keterampilan kolaborasi yang diamati meliputi kontribusi aktif, kerja produktif, fleksibilitas dan kompromi, tanggung jawab, sikap saling menghargai, serta komunikasi efektif. Hasil penelitian menunjukkan bahwa keterampilan kolaborasi siswa mengalami peningkatan setelah penerapan model PjBL berbasis STEM. Sebelum perlakuan, keterampilan kolaborasi siswa masih berada pada kategori sedang dan rendah, ditunjukkan oleh rendahnya partisipasi diskusi, kerja sama kelompok, tanggung jawab, dan komunikasi antarsiswa. Setelah perlakuan, hasil penilaian menunjukkan peningkatan pada seluruh indikator dengan kategori tinggi dan sangat tinggi. Hasil observasi menunjukkan indikator fleksibilitas dan kompromi memperoleh persentase tertinggi sebesar 97,5%, sedangkan komunikasi efektif mencapai 80%. Dengan demikian, penerapan model Project Based Learning berbasis STEM efektif dalam meningkatkan keterampilan kolaborasi siswa di SMP Yayasan Pendidikan Nurul Hasaniah.Kata Kunci: Keterampilan Kolaborasi, Project Based Learning (PjBL), STEM.