The aim of this study was to investigate the levels of secondary school students' knowledge about three Global Environmental Problems: Global Warming, Acid Rain, and Ozone Layer Depletion. 638 7th grade (N=316) and 8th grade (N=322) students enrolled in five different secondary schools participated in this study. The survey method was used to determine the levels of students' knowledge of three global environmental problems. In this study, drawings (separate for each topic) and open-ended questions specific to all three topics were used as data collection tools. The data obtained from drawings and open-ended questions were analyzed together and assessed based on three knowledge categories (informed view, transitional view, and naïve view). The results indicated that the levels of secondary school students' knowledge about three global environmental problems were low. It was also found that they held various misconceptions and their knowledge levels on each topic were close to each other. The results of the Pearson Correlation indicated that there was a significant relationship between the levels of secondary school students' knowledge about only GW and OLD, but a weak correlation. The results of MANOVA indicated that there was a significant difference in the mean scores of students' knowledge of GW from 8th to 7th-grade students, while there was a significant difference in favor of 8th-grade students with respect to the topics of AR and OLD.