Planned science activity (PSA) is compulsory in Vietnamese preschools, where children learn about science under the guidance of teachers who have prepared the content, materials, and process in advance. This case study investigates materials usage during PSAs at a public preschool in Da Nang, Vietnam, focusing on the types and how science materials are used. This study’s PSA-ECERS3 and PSA-SSTEW are adaptations of the original the Early Childhood Environment Rating Scale Third Edition (ECERS-3) and Sustain Shared Thinking and Emotional Well-being (SSTEW) scales. The results of these scales were presented as a qualitative report, complemented by illustrative instances of teaching methods from participant PSAs. The results showed that photos and slides on a computer about the objects of the PSA lesson were the most frequently used materials. Teachers used them to teach science concepts through on-site observation, question-and-answer sessions, and play. By contrast, teachers rarely used natural materials, experiments, or hands-on activities to help children learn about science. The results of ECERS-3 and SSTEW also indicated that PSAs with more interactive activities using the materials received higher scores than ones that did not include interaction.