Nonprofit organizations (NPOs) can provide services to disaster-impacted communities and residents in a more timely manner than the government can. The Wenchuan earthquake, which occurred on May 12, 2008, was the most severe natural disaster in China in recent years. NPOs participated in rescue and reconstruction efforts and were an important emergency response force, leading some to call 2008 “the first year of nonprofit organizations in China” (Yang, 2015). The most striking feature of NPOs’ participation in the Wenchuan earthquake relief efforts was that they set up different types of collaborations among themselves to better leverage limited resources and expand on the power of any single organization acting alone. This article differentiates between two types of nonprofit collaboration—contract-based and voluntary-based collaborations—and explores the factors that facilitated the formation of each type of collaboration following the Wenchuan earthquake. Based on three in-depth case studies of (1) Sichuan 5/12 Center for Voluntary Disaster Relief (CVDR), (2) the Sichuan Province NPOs Joint Office (SPNJO), and (3) the New Hometown Plan (NHP), we found that resource dependence, network effect, and volunteerism played different roles in the formation of the two types of collaboration. These findings lead to policy recommendations for improving nonprofit collaboration to respond to and recover from natural catastrophes.