The importance and popularity of interorganizational collaboration among nongovernmental organizations (NGOs) have grown considerably in recent years. Despite these growths, however, not much is known about why NGOs network the way they do or why NGO networks are structured the way they are. Using homophily theory and exponential random graph modeling, this study examines the patterns of interorganizational collaborative ties among infectious diseases international NGOs (INGOs) in 2007 (n = 94). The results suggest that these NGOs are more likely to collaborate when they have the same status, when they have similar (closer) founding dates, when they are headquartered in the same global hemisphere (north/south), when they have common funding partners, and when they are headquartered in the same geographic regions. Overall, the findings from this study suggest that various sources of homophily inform partner selection among infectious disease INGOs.