While research on K-12 environmental education (EE) has been quite robust, there has been less focus on effective approaches for mature-age adult learners. This qualitative study examined perceptions of barriers to sustainability in American, mature-age adult learners. Results revealed two interacting, superordinate themes: personal relevance and social environmental context, which each included several thematic barriers that resulted in a hypothesized model of internalized sustainable identity. This identity is the personal orientation/responsibility toward living a sustainable lifestyle and aligns with other environmentally-based identity models present in the literature. Implications for educators are discussed, including the recommendation to examine EE for mature-age adults through the lens of identity change.