Penelitian ini bertujuan untuk (1) menghasilkan LKPD IPA berbasis Problem Based Learning sebagai bahan ajar yang layak menurut dosen ahli dan guru IPA serta (2) mengetahui peningkatan keterampilan berpikir kritis peserta didik dengan menggunakan LKPD IPA. Penelitian ini merupakan penelitian dan pengembangan dengan model 4D. Prosedur pengembangan meliputi define, design, develop, dan disseminate. Instrumen penelitian meliputi lembar validasi kelayakan LKPD IPA oleh dosen ahli dan guru IPA, lembar observasi keterlaksanaan pembelajaran Problem Based Learning, lembar observasi keterampilan berpikir kritis, dan soal pretest-posttest keterampilan berpikir kritis. Teknik analisis data berupa analisis kualitatif dan kuantitatif. Hasil Penelitian diperoleh (1) LKPD IPA berbasis Problem Based Learning tema Pemanasan Global untuk meningkatkan keterampilan berpikir kritis dinyatakan layak oleh dosen ahli dan guru IPA dengan kategori sangat baik (A) serta (2) penguasaan keterampilan berpikir kritis melalui observasi yaitu pertemuan 1 dengan kategori cukup, pertemuan 2 dengan kategori sangat baik, dan pertemuan 3 dengan kategori sangat baik sedangkan melalui tes dengan kategori sedang.Kata kunci: Keterampilan Berpikir Kritis, LKPD IPA, Model Problem Based LearningThe aims of this research are to (1) develop science student worksheet based on Problem Based Learning as teaching material according university level instructor experts and natural science teacher and (2) to know the increace of critical thinking skill by using science student worksheet. This research is research and development which uses 4D model. The procedure of this research are define, design, develop, and disseminate. The instrument are validation sheet of science student worksheet, obsevation sheet of the implementation of Problem Based Learning, obsevation sheet of critical thinking skill, and pretest-posttest of critical thinking skill. The data analysis technique include qualitative and quantitative. The result of this research show that (1) science student worksheet based on Problem Based Learning on the theme Global Warming to increase critical thinking skill archieved by university level instructor experts and natural science teacher with excellent (A) category and (2) the increase of critical thinking skill using observation in the first meeting by enough category, in the second meeting by excellent category, and in the third meeting by excellent category while using pretest-posttest with gain score which is medium category.Keywords: Critical thinking skill, Problem Based Learning Model, Science student worksheet