Large-scale infrastructure projects contribute to economic development, connectivity, energy security, and social welfare. However, they can also generate substantial environmental and social impacts. This study examines how environmental and social sustainability are incorporated into large-scale infrastructure decision-making through a multiple-case study analysis of three major projects: the Jakarta–Bandung High-Speed Rail in Indonesia, the Belo Monte Dam in Brazil, and the Adani Carmichael Mine in Australia. The cases represent different infrastructure contexts and reveal recurring tensions between economic development objectives, environmental protection, community interests, and long-term sustainability. Through cross-case analysis, the study identifies common challenges including the prioritisation of economic and strategic objectives, limitations in stakeholder participation, ecological impacts, and inadequate consideration of long-term social and environmental consequences. The findings indicate that regulatory compliance and conventional project appraisal do not necessarily ensure sustainable or socially legitimate infrastructure outcomes. The study therefore highlights the need to embed environmental and social considerations throughout infrastructure planning, assessment, approval, and governance. It proposes strengthened stakeholder participation, sustainability and ethical assessments, adaptive decision-making, climate-impact accounting, and biodiversity and social safeguards as key governance measures. The study concludes that sustainable infrastructure requires decision-making approaches that move beyond project delivery and procedural compliance towards integrated environmental and social sustainability.