Transnational environmental law is the subject of growing scholarly interest. Yet, much work remains to be done to fill in both the conceptual and empirical contours of this field. One methodological challenge that transnational law poses is the need to look beyond traditional sources of international and national law. This article contributes to efforts to understand transnational law's multilayered architecture by drawing attention to the use of transnational contracts as a mechanism to protect habitats and species. The diverse and proliferating examples of conservation contracts discussed in this article – which include forest carbon agreements, conservation concessions, debt-for-nature swaps, conservation performance payments, and private protected area agreements – reveal an ongoing and intensifying transnational attempt to use private contracts to address some of the most pressing issues of common concern. This article draws on fairness theory in both contract and international environmental law to argue for law's relevance in interpreting conservation's call for contracts.