The children of Mexican immigrants face formidable barriers to achieving socioeconomic mobility due to their parents’ precarious economic position and high rates of unauthorized status. In the short term, Mexican immigrants often coreside in extended household living arrangements with extended kin and unrelated friends and associates to shelter themselves from economic deprivation and insecurity of unauthorized status. Using individual-level Census data, the present study examines how family economic resources relate to household living arrangements. The results are consistent with various theories of immigrant household formation, especially those that explain household structure in terms of economic need and processes of immigration. Families residing in extended arrangements are unique, however, in terms of how often they include a householder and how much they contribute to total household resources, indicators that families may hold more supportive roles within extended households. The implications of the findings for the well-being of immigration children are discussed.