Climate auctions—a 21st-century alternative— competitively allocate public funding to commercially developed mitigation projects, ensuring both transparency in selection processes and efficiency in leveraging investment. Climate auctions offer successful project developers and commercial entities a guaranteed price for verified emission reductions, which these entities can then use to raise additional finance. This brief explores why climate auctions are an effective tool for achieving climate outcomes, focusing on how developing country policymakers can utilize auctions to accelerate NDC implementation and raise climate ambition. It then outlines how climate auctions work and where they are most effective in achieving climate outcomes.