BACKGROUND AND OBJECTIVES: This study explores the association between informal caregiving for older adults and environmentally sustainable behaviors across the 27 European Union countries, aiming to identify how the gendered and domestic nature of environmentalism relates to senior care. RESEARCH DESIGN AND METHODS: Data from 41,742 respondents aged 16-74 were analyzed from the Survey of Gender Gaps in Unpaid Care, Individual and Social Activities, and conducted by a scientific consortium in 2022. Frequency of sustainable behaviors was measured across 10 indicators. Multilevel mixed-effects linear regressions examined associations between caregiving and sustainable behaviors, adjusting for demographic, socioeconomic, and attitudinal covariates. RESULTS: Informal caregivers engaged in eco-friendly actions significantly more frequently than noncaregivers across all 10 sustainable-behavior indicators ( DISCUSSION AND IMPLICATIONS: This is the first large-scale cross-national study that demonstrates a consistent association between older-adult caregiving and a wide range of environmentally sustainable behaviors. Results suggest the experience of caring for a vulnerable family member is closely related to a broader sense of social and environmental responsibility. Caregivers' heightened engagement in sustainable consumption positions them as potential early adopters and change makers. Findings highlight new avenues for environmental education and caregiver support initiatives that synergistically promote interpersonal and environmental care.