The expansion of precarious work in recent decades has motivated a large body of research on its implications for health. While considerable work has focused on whether precarious work undermines health, much less is known about why it matters. To fill this gap, this paper offers and tests a conceptual model whereby the effects of precarious work on health are mediated by social marginality, specifically reduced self-efficacy, weaker social integration, and lower social capital. All three mechanisms are understood as both social consequences of precarious work and important determinants of health. Empirically, we use data from the European Social Survey and investigate (1) conditional direct effects of precarious work on self-rated health and (2) extent of mediation via the threemechanisms. Furthermore, we assess the generalizability of the model across five welfare state regimes that prior work has deemed to be important moderators of the health-precarious work relationship. Results indicate precarious work has significant conditional direct effects and indirect effects through all three mediators that significantly reduce effect of precarious work on health. This is robust in the general sample and for four of five welfare state regimes. These findings highlight a previously unexplored vector connecting precarious work to health and indicate that the effects of precarious work on perceptions of self and social relations is a key link to poorer health. The study also expands conceptualization of the broad role of socioeconomic status for health inequalities and furthers understanding of the mechanisms at work.