This study investigated the extent to which junior secondary school students in Port Harcourt Local Government Area of Rivers State Nigeria are aware of issues related to climate change and sustainable development. The study adopted a descriptive survey design. Four research questions were raised. Two instruments were used for data collection, a questionnaire and the junior secondary school teaching syllabus. The questionnaire titled " Climate change and Sustainable Development Awareness Questionnaire" (CCSDA) was used to obtain data from 1600 junior secondary school three (JSS3) students from the fourteen junior secondary schools in Port Harcourt Local Government of Rivers State, Nigeria. The questionnaire had three sections; A, B and C. Section A obtained the demographic features and bio-data of students, section B obtained information on the awareness level of climate change while section C obtained information on sustainable development awareness level. Simple percentages and mean were used to answer the research questions. The results from the data analysis revealed among other things that the JSS curriculum coverage of climate change is small; there is no sustainable development issues in the teaching syllabus of JSS; the level of awareness of sustainable Development issues is low; even though the climate change issues awareness level is high but the knowledge is low; students are eager and willing to know more about climate change and sustainable development issues. Based on these results, the researcher recommended among other things that more themes on Climate change and sustainable development should be introduced in social studies and integrated science in all the JSS level. Having very few topics on climate change and none at all on sustainable development at the junior secondary level is dangerous at this level of their development and more especially now that the world is striving to attain the Millennium Development Goals (MDGs).