Penggunaan Lembar Kerja Peserta Didik (LKPD) di tingkat sekolah dasar masih rendah, hanya sekitar 30%, padahal LKPD dapat mempermudah proses pembelajaran dan melatih keterampilan proses sains (KPS) siswa. KPS penting ditanamkan sejak dini karena merupakan dasar dalam menerapkan metode ilmiah serta pengembangan keterampilan lainnya. Penelitian ini bertujuan untuk: (1) Menghasilkan LKPD berbasis Project Based Learning (PjBL) yang layak digunakan untuk meningkatkan KPS dalam praktikum IPAS di SDN Trijaya, dan (2) Menguji efektivitas LKPD berbasis PjBL tersebut dalam meningkatkan KPS siswa. Metode yang digunakan adalah penelitian dan pengembangan (R&D) dengan mengacu pada model Borg and Gall yang meliputi tahap studi pendahuluan, pengembangan, serta pengujian dan diseminasi. Subjek penelitian adalah 16 siswa kelas V di SDN Trijaya, Kuningan, Jawa Barat. Teknik pengumpulan data meliputi wawancara, observasi, serta validasi produk oleh ahli materi, ahli media, dan guru kelas. Validitas produk dianalisis menggunakan Aiken’s V, dan efektivitas diuji menggunakan observasi serta uji paired sample t-test. Hasil penelitian menunjukkan bahwa LKPD berbasis PjBL dikategorikan sangat layak dengan skor Aiken’s V rata-rata sebesar 0,95. Uji perbedaan menunjukkan bahwa LKPD ini mampu meningkatkan KPS siswa, dibuktikan dengan nilai t-hitung sebesar 33,33 yang lebih besar dari t-tabel 2,13145. Dengan demikian, LKPD berbasis PjBL yang dikembangkan dinyatakan layak dan efektif dalam meningkatkan keterampilan proses sains siswa sekolah dasar

The use of Student Worksheets (LKPD) in elementary schools remains low, at only around 30%, despite their potential to facilitate learning and improve students’ science process skills (SPS). SPS are essential to be introduced from an early age, as they form the foundation for applying scientific methods and developing other skills. This study aims to: (1) Develop a Project-Based Learning (PjBL)-based LKPD that is feasible for improving SPS in science practicum activities at SDN Trijaya; and (2) Test the effectiveness of the developed LKPD in enhancing students’ SPS. The research uses a Research and Development (R&D) method, referring to the Borg and Gall development model, which includes preliminary study, development, testing, and dissemination. The research subjects consisted of 16 fifth-grade students at SDN Trijaya, Kuningan, West Java. Data collection techniques included interviews, observations, and product validation by subject matter experts, media experts, and class teachers. Product validity was analyzed using Aiken’s V, while effectiveness was tested through observation and an paired sample t-test. The results showed that the PjBL-based LKPD was categorized as highly feasible, with an average Aiken’s V score of 0.95. The effectiveness test indicated a significant improvement in students’ SPS, as evidenced by a t-count of 33,33, which is greater than the t-table value of 2.13145. Thus, the developed PjBL-based LKPD is deemed both feasible and effective in enhancing elementary school students’ science process skills.