The purpose of the study was to explore Turkish primary science teacher candidates' understanding of global warming and ozone layer depletion. In the study, as the research approach the survey method was used. The sample consisted of one hundred eighty nine third grade science teacher candidates. Data was collected using the tool developed by the researcher. The survey solicited written opinion responses to seven open-ended questions. Teacher candidates' written opinions about global warming and ozone layer depletion were analyzed descriptively. The results of the analysis were presented as percentages and frequency. The findings suggest that prospective teachers' understandings about these issues were limited and they had some significant common, misconceptions. Finally, the findings were discussed in comparison with the previous research with respect to environmental education.