Sustainable infrastructure for the Amazon requires a recognition of the region’s vast natural capital and unique importance for the world. The Amazon stores 120 billion tons of carbon, supports rainfall systems that are critical for regional economies, and provides habitat for one-third of the world’s species. Investments to secure the Amazon’s natural capital are an essential step to supporting sustainable infrastructure, and infrastructure planning should consider both natural and traditional (gray) infrastructure. We propose that the G20, and the Development Finance Institutions, promote conditions for quality and sustainable infrastructure investment by: (1) Supporting international public and private commitments and funding mechanisms to bolster Amazon countries’ progress in conserving forests, securing natural capital, and promoting sustainable development; (2) Supporting sustainable infrastructure policies and guidelines that fully incorporate social and environmental costs for project selection and preparation;  (3) Establishing lending principles that infrastructure investment must be compatible with land and water conservation and healthy ecosystems, with recognition of the role of nature-based infrastructure; and (4) Promoting local bio-economies aligned with goals for securing the Amazon’s natural capital.