<p>Young adults experiencing homelessness (YAEH) are significantly more likely to engage in HIV risk-related sexual behavior relative to their stably housed peers, and their social support networks can influence their engagement in these behaviors. However, few studies have investigated HIV risk behaviors among YAEH who are “couch-surfing,” a highly prevalent network-based survival strategy that involves cycling through temporary, informal housing arrangements. The current study utilizes survey data collected from 461 YAEH accessing drop-in center services in Los Angeles, California, between September 2016 and October 2018. Egocentric network analysis was used to examine associations among couch-surfing, sources of social support, and HIV risk and prevention behaviors. The potential moderating effect of social support on the relationship between couch-surfing and specific sexual risk behaviors was also tested. Compared to street- and shelter-based youth, couch-surfing YAEH reported the highest rates of recent transactional sex (18.0%) and concurrent or serial sexual partners (38.2%). Relative to residing in emergency shelter or transitional housing programs, couch-surfing was associated with over twice the odds of engaging in recent transactional sex (OR = 2.52, <i>p</i> = .023, 95% CI 1.13–5.62)—as was living unsheltered (OR = 2.06, <i>p</i> = .029, 95% CI 1.08–3.95). While social support was individually associated with several HIV risk-related sexual behaviors, its effect was ultimately eclipsed by homeless situation in the final model. Findings underscore the need for individual- and structural-level interventions that attend to the unique socioenvironmental contexts of couch-surfing YAEH.</p>