Abstract: This research aims to produce student worksheets oriented to Problem-Based Learning (PBL) to improve students critical thinking skills on redox reaction material that is feasible in terms of validity, practicality, and effectiveness. This research is a Research and Development (R&D) study using the 4D development model, which was limited to the development stage and a limited trial with 25 students from Senior High School 1 Sooko Mojokerto.