Social capital is recognised as an important resource for people experiencing poverty, yet conceptualisations of its relationship to homelessness are underdeveloped. Some studies show that social capital can protect against the risk of homelessness, whilst others show that reliance on social capital by people already experiencing homelessness rarely enables them to exit homelessness and can in fact render them vulnerable to exploitation and abuse. Building on these insights, we develop a framework for conceptualising the relationship between stable housing and social capital. Drawing on analysis of qualitative interviews with people experiencing homelessness in London, we demonstrate how, in the absence of stable housing, people experiencing homelessness lack key conditions that enable the accumulation and effective use of social capital. These include the ability to practice reciprocity, achieve recognition, and exercise autonomy in social relationships. We conclude that stable housing is a precondition for utilising social capital to ameliorate, rather than exacerbate, vulnerability, lending further evidence to support Housing First policies.