<![CDATA[The low levels of critical thinking and problem-solving skills among students remain a challenge in science learning. This condition is influenced by the use of conventional learning methods and limited textbook materials, which have not facilitated active student involvement in problem-solving. This study aims to evaluate the validity, practicality, and effectiveness of problem-solving-based science teaching materials in improving students' critical thinking and problem-solving skills. This study is a research and development (R&D) using the ADDIE model, which includes the stages of analysis, design, development, implementation, and evaluation. The subjects were 25 fifth-grade elementary school students. Data collection was carried out through expert validation, questionnaire distribution, and instrument-based tests consisting of validation sheets, practicality questionnaires, and tests of critical thinking and problem-solving ability. Data were analyzed qualitatively and quantitatively to assess the quality of the developed product. The results of the study indicate that the problem-solving-based science teaching materials meet the criteria of being very valid, very practical, and effective in improving students' critical thinking and problem-solving abilities. Thus, the developed teaching materials are suitable for use in science learning. This research suggests that problem-solving-based science teaching materials can serve as learning tools, especially for ecosystem material, to support learning oriented towards developing students' high-level thinking skills.]]>
