This article reviews ever published quantitative evidence on in-work poverty and family demographic processes in OECD and EU-28 countries. Despite the increasing attention to in-work poverty in Europe and beyond, a comprehensive and critical review on how family demographic processes shape in-work poverty risks is still missing. In this systematic review, we first provide a quantitative review of results from analyses that estimated the association between in-work poverty and parental home leaving, union formation, marriage, parenthood, and dissolution of non-marital and marital unions. This allows us to formulate tentative conclusions about whether and in which direction family demographic processes are associated with in-work poverty. Second, we discuss in detail conceptual and methodological advances in in-work poverty research, that is analyses that deviated from the more conventional approaches adopted in the analyses selected for the quantitative review or that accounted for the interaction between family demographic processes and individual or context characteristics. Our review highlights theoretical and methodological challenges for future studies linking in-work poverty and family demography.