Recent research on start-up accelerators has drawn attention to the central importance of social resource exchange among peers for entrepreneurial success. But such peer relationships contain both cooperative and competitive elements, making accelerators a prime example of a mixed-motive context in which successful generalized exchange—unilateral giving without expectations of direct reciprocity—is not a given. In our ethnographic study of a Silicon Valley accelerator, we sought to explore how generalized exchange emerges and evolves over time. Employing an abductive, sequential mixed-methods approach, we develop a process model that helps explain how a system of generalized exchange may or may not emerge. At the core of this model are the interaction rituals within social events that come to create distinct exchange expectations, which are either aligned or incompatible with generalized exchange, resulting in fulfilled or failed exchanges in subsequent encounters. Whereas fulfilled exchanges can kickstart virtuous exchange dynamics and a thriving generalized exchange system, failed exchanges trigger vicious exchange dynamics and an unstable social order. These findings bring clarity to the puzzle of how some generalized exchange systems overcome the social dilemma in mixed-motive contexts by highlighting the central role of alignment between structure and process.