Abstract: This research aims to develop scientific student worksheet based on indicators of critical thinking skills. This research uses Research and Development (R&D) method with one group pre-test post-test design. The results showed 86.35% reliability, 92.64% validity, and 95.38% readability. N-gain analysis reached high value criteria at indicator of questioning, responding, analyzing and conducting scientific experiments. Student activity dominant with worksheet duties (73.93% and 71.37%) and conducting scientific experiment (75.74% and 73.44%). It can be concluded that the student worksheet meet the criteria of validity, practicality and effectiveness for practice the student scientific ability and critical thinking skills.Keywords : student worksheet, scientific; critical thinking, primary school.Abstrak: Penelitian ini bertujuan mengembangkan LKS saintifik berdasarkan indikator keterampilan berpikir kritis. Penelitian ini menggunakan metode Research and Development (R&D) dengan desain penelitian one group pre-test post-test design. Hasil penelitian menunjukkan persentase reliabilitas 86,35%; validitas 92,64%; dan keterbacaan 95,38%. Analisis n-gain berkriteria tinggi ditunjukkan pada indikator menanya, menanggapi pertanyaan, menganalisis dan melakukan percobaan ilmiah. Aktivitas siswa dominan pada kegiatan mengerjakan LKS (73,93% dan 71,37%) dan melakukan percobaan ilmiah (75,74% dan 73,44%). Berdasarkan temuan penelitian dapat disimpulkan bahwa LKS memenuhi kriteria validitas, kepraktisan dan keefektifan sehingga layak untuk melatihkan kemampuan saintifik dan keterampilan berpikir kritis siswa.Kata Kunci : LKS, saintifik, berpikir kritis, SD