Objective: To evaluate the feasibility and utility of integrating environmental sustainability into healthcare decision-making through a novel "health-economic-climate" model, using depression care in France as a case study. Design: A cost-utility analysis incorporating clinical, economic, and carbon footprint data. A semi-Markovian state-transition model with a five-year time horizon was developed to assess three primary depression treatment strategies: antidepressants (AD), psychotherapy (PT), and combined therapy (COMB). Carbon emissions were monetized using the social cost of carbon. Setting: The French healthcare system, with direct medical costs and environmental impacts analyzed from a system-level perspective. Participants: A virtual cohort of patients experiencing a first episode of depression, transitioning between health states over time based on treatment modality. Interventions: Three treatment strategies for depression were compared: AD, PT, and COMB. Main Outcome Measures: Incremental cost-effectiveness ratios (ICER) in € per quality-adjusted life year (QALY) gained, alongside carbon footprints expressed as kg of carbon dioxide equivalent emissions per patient per year. 1 Results: PT was the least costly strategy over five years, with AD showing no additional benefit despite higher costs. COMB demonstrated superior clinical outcomes but at a higher cost, with an ICER of €35,422/QALY. Carbon emissions contributed little to overall costs across strategies, accounting for approximately 4% of total expenses. Sensitivity analyses showed that reducing the duration of antidepressant use significantly improved COMB's cost-effectiveness. The integration of carbon emissions into decision modeling provided an additional perspective without altering the overall conclusions. Conclusions: This study demonstrates the feasibility of integrating environmental sustainability into healthcare decision models. By combining clinical, economic, and carbon impact data, the proposed framework offers practical insights for decision-makers and healthcare practitioners. These findings provide an opportunity to align healthcare priorities with environmental goals, emphasizing sustainability as a core component of quality care.