Children of foreign-born parents with vulnerable legal status, limited economic rights and exclusion from national social interventions may be at higher risk for severe acute malnutrition (SAM). We evaluated the relationship between parent status (foreign-born vs. South African) and outcomes for children with SAM admitted to a rural regional hospital in the Western Cape, South Africa. A retrospective cohort study was conducted including children <5 years admitted to Worcester Provincial Hospital during 2015-17 with SAM (WHO weight-for-height Z score <-3, presence of nutritional oedema, mid-upper-arm-circumference of <11.5 cm or visible severe wasting). Exposures, including parent status, and outcomes including in-hospital death were determined from hospital and regional dietician records. Of 95 children included, 31 (33%) were of foreign-born and 64 (67%) of South African parents. Median (interquartile range) age at admission was 12 (8-18) vs. 10 (8-13) months in children of South African vs. foreign-born parents with no difference in preterm birth, concurrent illnesses or admission duration. Age, HIV status and breastfeeding practices were no different in foreign-born compared to South African mothers. In-hospital deaths occurred in 3/64 (5%) and 6/31 (19%) children of South African vs. foreign-born parents (p = 0.01). Children of foreign-born compared to South African parents had an odds ratio of 4.88 (95% CI 1.13-21.06) for in-hospital SAM-associated mortality. In this rural setting, 33% of children admitted with SAM were of foreign-born parents and experienced in-hospital SAM-associated mortality at least four times higher than children of South African parents. This illustrates the extreme vulnerability of these children.