Background: Middle-aged and older adults play an important role in the provision of informal support, however, the impact on the health of those individuals who provide informal care is unclear. The main objectives of this study are: (1) to assess the prevalence of co-residential caregiving provided by individuals aged 50+; (2) to analyze differences between the group of Portuguese co-residential caregivers and the group of Portuguese non-caregivers; (3) to examine the longitudinal effect of providing informal care on the health of co-residential informal caregivers in Portugal. Methods: Data from wave 4 and wave 6 of the Survey of Health Ageing and Retirement in Europe (SHARE) were used. A linear mixed model and a generalized mixed model were used to analyze the longitudinal effect of providing informal care on the health (physical health and depressive symptoms) of Portuguese individuals aged 50 + . Results: In both SHARE waves analyzed, Portugal had the highest percentage of co-residential caregivers aged 50+. At baseline, the Portuguese co-residential caregiver population, compared to non-caregivers, has a lower percentage of employed individuals (14.9% compared to 25.7%) and a higher percentage of individuals with four or more depressive symptoms (56.4% compared to 35.5%). The caregivers also have a lower quality of life (CASP-12) (30.93 compared to 32.59). Marginal differences in educational levels between the caregiver and non-caregiver groups were also found, with co-residential caregivers having lower levels of education (72.3% have ISCED 0-2 compared to 64.7%), lower levels of cognitive function (- 2.321 compared to - 1.784), lower levels of physical health (- 0.180 compared to - 0.076) and lower engagement in moderate or vigorous physical activity (14.9% compared to 21.5%). Longitudinal models reveal that providing care within the household is not associated with physical health (b = 0.048; se = 0.035; p = 0.167), but is associated with depressive symptoms (OR = 1.609; 95% CI = 1.141-2.271; p = < 0.010). Conclusions: Portugal has the highest percentage of co-residential caregivers aged 50+. In that country, providing informal care to a household member is associated with depressive symptoms. Portuguese policymakers should therefore promote programs to prevent and alleviate the depressive symptoms experienced by individuals aged 50+, who provide co-residential care.