Background The healthcare sector contributes ~5% of global greenhouse gas emissions, with medicines responsible for ~10% throughout their lifecycle. Understanding how the environmental impact of medicines influences patients’ preferences relative to ease of use and cost supports interventions promoting appropriate medicine consumption, reduced waste, and environmental sustainability. Objective To investigate patient preferences and attitudes regarding the environmental impact of medicines in relation to ease of use and cost. Methods A cross-sectional survey (Dec 2022–Jan 2023) was conducted using the Dutch AMP pharmacy panel (>25,000 chronic medicine users). It included a discrete choice experiment (DCE) on medicines’ environmental impact, ease of use, and cost, and questions on environmental sustainability in medicine use and daily life. Latent class analysis identified groups with shared preferences. An environmental sustainability attitude score was calculated from daily life behavior. Results Of 25,787 invited panel members, 6,390 responded (24.8%), with 4,122 respondents included in the analysis (16.0%; mean age 68 years; 42.6% female). Four preference groups were identified: Eco-focused (55.7%), Cost-focused (20.1%), Indifferent (16.4%), and Eco-skeptical (7.8%). Environmental sustainability attitude scores were highest in the Eco-focused and Eco-skeptical (median 75.0%), followed by Indifferent and Cost-focused (median 66.7%). Important factors influencing this were environmental concerns (Eco-focused), environmental and personal health concerns (Eco-skeptical), costs (Cost-focused), and environmental, cost, and personal health concerns (Indifferent). Only 8.8–15.5% had good or very good knowledge about the environmental impact of medicines. Conclusion Environmental sustainability significantly affects medicine preferences, though heterogeneity exists. Tailored initiatives are required to promote environmentally sustainable pharmaceutical care.