This study aims to obtain data on the feasibility of problem-solving-based test instruments to foster the creative thinking skills of junior high school students on environmental conservation. The method used in this study is Research & Development (R&D) with development procedures according to Sugiyono. This study was conducted in 5 stages: potentials and problems, data collection, product design, design validation, and design revision. The instrument used in this development research is a question validation sheet of material experts, evaluation experts, and expert practitioners. The results showed that based on the assessments of content experts, evaluation experts, and practitioners, scores of 88.4%, 88.6%, and 89.9% were obtained, which were classified in the "Very Feasible" category, respectively. In conclusion, the overall validation of the problem-solving-based test instrument received a score of 88.9%, which belongs to the "Very Feasible" category, so the test instrument can be used as an alternative tool for evaluating science learning for junior high school students with several revisions.