Data on both the provision and receipt of informal care among populations of older adults are limited. Patterns of both informal care provided and received by older adults in the Republic of Ireland (RoI) and Northern Ireland (NI) were evaluated. A cross-sectional community-based population survey was conducted. Randomly selected older people (aged 65+, n = 2033, mean age (standard deviation): 74.1 years (6.8), 43% men, 68% response rate) provided information on the provision and receipt of care, its location, and the person(s) who provided the care. Twelve per cent of the sample (251/2033) identified themselves as informal caregivers (8% RoI and 17% NI). Caregivers were more likely to be women, married, have less education and have less functional impairment. Forty-nine per cent (1033/2033, 49% RoI and 48% NI) reported receiving some form of care in the past year. Care recipients were more likely to be older, married, have more functional impairment, and poorer self-rated health. Receiving regular informal care (help at least once a week) from a non-resident relative was the most common form of help received [28% overall (578/2033); 27% RoI and 30% NI]. Five per cent (n = 102/2033) of the sample reported both providing and receiving informal care. Levels of informal care provided by community-dwelling older adults were notably higher than reported in single-item national census questions. The balance of formal and informal health and social care will become increasingly important as populations age. It is essential, therefore, to evaluate factors facilitating or impeding informal care delivery.