Background: The seating arrangement of in-center hemodialysis is conducive to patients forming a relationship and a social network. We examined how in-center hemodialysis clinic seating affected patients forming relationships, whether patients formed relationships with others who have similar transplant behaviors (homophily), and whether these relationships influenced patients (social contagion) to request a living donation from family and friends outside of the clinic. Methods: In this 30-month prospective cohort study, we observed the relationships of 46 hemodialysis patients in a hemodialysis clinic. Repeated participant surveys assessed in-center transplant discussions and living donor requests. A separable temporal exponential random graph model estimated how seating, demographics, in-center transplant discussions, and living donor requests affected relationship formation via sociality and homophily. We examined whether donation requests spread via social contagion using a susceptibility-infected model. Results: For every seat apart, the odds of participants forming a relationship decreased (OR 0.74, 95% confidence interval CI [0.61, 0.90], p = 0.002). Those who requested a living donation tended to form relationships more than those who did not (sociality, OR 1.6, CI 95% [1.02, 2.6]; p = 0.04). Participants who discussed transplantation in-center were more likely to form a relationship with another participant who discussed transplantation than with someone who did not discuss transplantation (homophily, OR 1.9, CI 95% [1.03, 3.5]; p = 0.04). Five of the 36 susceptible participants made a request after forming a relationship with another patient. Conclusions: Participants formed relationships with those whom they sat next to and had similar transplant behaviors. The observed increase in in-center transplant discussions and living donation requests by the hemodialysis clinic social network members was not because of social contagion. Instead, participants who requested a living donation were more social, formed more relationships within the clinic, and discussed transplantation with each other as a function of health-behavior homophily.