Global supply chains enhance value, but are subject to governance problems and encourage evasive practices that deter sustainability, especially in developing countries. This article proposes that the precontractual environment, where parties are interested in trade but have not yet negotiated formal terms, can enable a unique process for building long-term sustainable relations. We argue that precontractual signals based on relation-specific investments, promises of repeated exchange, and reassuring cheap talk can be leveraged in precontract by the power of framing. We show how these framing signals are amplified in precontract because the lack of credible information, minimal time for reflection, and the role of risk-aversion present in supply chain contract negotiations. The result is a process that is uniquely productive for building long-term and valuegenerating contractual relations in supply chains, particularly in skeptical or even hostile negotiating contexts. We then show how framed precontractual signals generate a joint contractual surplus through a supernormal profit known as a relational rent. This rent can be invested to improve sustainable practices, an efficient option in a competitive market due to the second order effects that sustainable practices generate. This novel process we propose thus potentially generates superior returns to other trust measures and encourages focus on precontract as a fertile environment for building sustainable investments. Keywords Sustainability • Global supply chains • Precontract • Framing • Developing countries Sustainability is an important component of multi-tier global supply chains (Levy et al. 2015). 1 There is evidence that sustainable supply chains improve product quality (Van der Vorst et al. 2009), unlock new markets (Hassini et al. 2012), increase consumer engagement (Linton et al. 2007), and deliver superior economic performance (Rao and Holt 2005). Sustainability in global supply chains is also of pressing social importance, impacting the health, safety, human rights, and economic development of workers (Maloni and Brown 2006). Sustainable practices also influence important environmental challenges such as climate change, pollution, and hyper-exploitation of non-renewable resources (Linton et al. 2007). As a result, a growing literature has emerged