This study aimed to examine the understanding of secondary school students about green chemistry-related concepts, to include raw materials, solvent, and atom economy. Interviews were conducted with secondary school students from Grades 9 to 12 to acquire their descriptive understanding of the corresponding concepts. Based on the systematic analysis of the collected data, a semi-structured two-tier diagnostic instrument was proposed, which was then administered to secondary school students. Some options that were less often selected by respondents were eliminated. Using the revised instrument, a pilot survey was conducted among secondary school students, and the similar elimination procedure was followed. The final instrument was used to conduct a survey among secondary school students from Grades 9 to 12 for examining their understanding of various concepts related to green chemistry. The results showed that secondary school students' understanding of green chemistry-related concepts and the term "green chemistry" was low. However, the older students' understanding of the corresponding concepts was significantly superior to that of the younger students. No noticeable differences were found between male and female students. The findings of this study can help teachers to better examine the knowledge mastered by their students and evaluate progression in learning green chemistry.