The UK Government has highlighted the need to develop appropriate information and support services for informal carers. Previous research that has investigated informal caring has found that managing medication is one aspect of the caring role that presents its own problems; however, these have not been subject to detailed examination. The objective of the present paper was to report the number and type of problems experienced by informal carers when managing medication for older care recipients, and to relate these to measures of coping and health. This was a cross-sectional survey undertaken in one district in each of four randomly selected health authority areas in England. Structured interviews, comprising closed and open questions, with 184 informal carers and 93 associated older care recipients were conducted in participants’ own homes. Data were gathered on the number and type of medication-related problems experienced in relation to the informal caring role, and the impact of these from carers’ perspectives in terms of coping and health. Sixty-seven per cent of carers reported problems with at least one medication-related activity. Problems were associated with all types of medication-related activities, and experienced by carers providing different levels of care for older people. Four themes were identified from carers’ accounts which illustrated a diversity of practical problems and anxieties: maintaining continuous supplies of medication in the home; assisting with administration; making clinical judgements; and communicating with care recipients and health professionals. Carers reporting greater numbers of medication-related problems were more likely to experience higher levels of carer strain (P < 0.001) and poorer mental health status (P < 0.001). The findings of the present study provide insights to inform the development of primary care services to support informal carers in the management of medication for older people.