“Collective impact” is a relatively new terminology emerging out of the philanthropic community for describing structured collaboration among parties who are focused on alleviating a particular social ill. Branded as “a way to better utilize resources and identify effective practices,” a collective impact initiative (CII) intentionally recruits actors from diverse industries and with diverse perspectives to focus on a specific social ill. In many respects, collective impact participants “agree to agree” over the course of an ongoing relationship. Collective impact is in early stages, and barriers to effectiveness are emerging, such as the absence of a contractual framework. Typical CIIs are managed through the strength of the parties’ relationships, not through a written agreement. This Article argues that the collective impact process is best understood through a relational contract context—a contract law theory that looks beyond the parties’ privity to consider the intent and relationships among the parties. More specifically, this Article lays the groundwork for impact transaction—large-scale social change by agreement— by building a framework for drafting relational contracts to enhance the likelihood of the sustainability of CIIs and impact transaction strategies, generally.