Penelitian ini merupakan penelitian dan pengembangan (Research and Development), yang bertujuan untuk mengetahui tingkat kelayakan dan kepraktisan. Prosedur pengembangan yang digunakan adalah model ADDIE (Analysis, Design, Development, Implementations, and Evaluation). Produk dinilai oleh 2 orang ahli , yaitu ahli evaluasi dan ahli materi. Selanjutnya dilakukan uji kepraktisan produk kepada 3 guru IPA di SMP negeri 2 Tarakan. Instrumen Penilaian Portofolio yang dikembangkan terdiri atas Sampul, rubrik afektif, kognitif, psikomotorik, lembar observasi, lembar penilaian , dan format menyusun laporan dan makalah. Kualitas Instrumen Penilaian Portofolio dinyatakan layak oleh ahli evaluasi dengan persentase penilaian sebesar 80% (layak) dan ahli materi dengan persentase penilaian sebesar 78,57% (layak), dan ahli praktisi guru IPA dengan persentase penilaian sebesar 86,66% (sangat praktis). Hasil penilaian ahli menunjukan bahwa Instrumen Penilaian Portofolio yang dikembangkan layak dan praktis untuk digunakan.

This research is research and development, which aims to determine the level of feasibility and practicality. The development procedure used is the ADDIE model (Analysis, Design, Development, Implementation, and Evaluation). Products are assessed by 2 experts, namely evaluation experts, and material experts. Furthermore, the product practicality test was carried out for 3 science teachers in Tarakan State Junior High School 2. The Portfolio Assessment Instrument that was developed consisted of front cover, affective assessment rubric, cognitive assessment, psychomotor assessment, contained observation sheet, and contained assessment sheet and format in compiling reports and papers. The quality of the Portfolio Assessment Instrument was declared feasible by evaluation experts with an appraisal percentage of 80% (feasible), and material experts with an appraisal percentage of 78.57% (feasible), and expert science teacher practitioners with an assessment percentage of 89% (very practical). The expert assessment results show that the Portfolio Assessment Instrument developed is feasible and practical to use.