A survey covering the scientific and social aspects of climate change was administered to examine U.S. undergraduate student mental models, and compare knowledge between groups based on major and environmental group membership. A Knowledge Score (scale 0–35, mean score = 17.84) was generated for respondents at two, central East Coast, U.S. universities (n = 465). Elements of student mental models examined include environmental issue confusion, skepticism, and self-reported understanding. This study finds that students frequently confuse climate change with other environmental issues, and that a substantial majority of students do not have an understanding of climate change that closely matches the scientific model. These misconceptions extend to their understanding of mitigation actions. Environmental group membership is shown to be a greater determinant of climate change knowledge than enrollment in a science major.