The Senior Help Line in Ireland provides a confidential telephone listening service for socially-excluded older people and is operated by older volunteers. The service has grown rapidly in recent years and is highly regarded as an important service for older people in the country. This paper provides a systematic examination and assessment of the service, from the perspectives of costs, outcomes and best practice. The study uses personal interviews, focus groups and postal questionnaires to elicit information about the service and its impact on volunteers and callers. The Senior Help Line has made a significant contribution to the health and wellbeing of older people in Ireland at relatively low cost. The service demonstrates the positive effects of volunteering for older people, and the value and effectiveness of peer-to-peer communication for vulnerable callers. The help-line is a model project in terms of accountability and best practice, but requires additional resources, particularly for publicity and training. It needs to become a branded national service for vulnerable older people to meet the level of need for a service of this kind. The help-line also needs to be linked more formally to existing health and social care provision for older people, to become part of a holistic model of healthy ageing for older people. For the service to reach its manifest potential, the efforts of the volunteers need to be supported by higher and sustained levels of public spending, through more widespread and substantial public-voluntary partnership arrangements.