This paper is the first assessment of the causal relationship between social capital and individual health in Mexico. Mexico has the second highest income inequality among working-age people in the OECD, and the second highest level of corruption, a widespread informal economy, while access to health services has only recently begun to have the pretention of universal coverage. This setting is propitious for the appearance of either small or wide networks and relationships that through mutual trust and reciprocity fills the absence of a complete social security system. Relationships between social capital and health may therefore be different from what has been found in the US, Europe, and Argentina. We use data from the first wave of the Mexican Family Life Survey (MxFLS-2002), with a nationally representative sample of 8.440 households from 150 villages in the country. We estimate the causal effect of individual-level social capital on selfassessed health, measured as a binary variable, using measures of formal and informal social interactions as indicators of social capital. In particular, we construct measures for trust (crime and victimization), participation in the community, social isolation (loneliness), caregiving activities, and access to informal credits. We account for the potential endogeneity of social capital through instrumental variable techniques, but find that our social capital indicators can be considered exogenous. Results suggest that the macro indicators (trust, participation, absence of social isolation) have a positive effect on health, but that the impact of micro indicators (caregiving, informal credits) is negligible.