Initiatives that bridge the fields of ageing and disability are considered critical internationally but to be limited in practice. Taking Ireland as a case, and focusing on social care, this article reports on a study investigating the separate organization of older people's and disability services as perceived by those working in policy-making, service provision and advocacy. In Ireland, as in many countries, social care is administered separately for disabled people and older people. Perceptions of those working in social care are thought to play a role in successful boundary-crossing initiatives. This study suggests that while participants often perceived the administrative and funding boundary between the fields of ageing and disability as illogical, inflexible, and not delivering person-centred care or support, the divide between the two sectors is underpinned by conceptual issues, including the lack of a concept of disability with ageing. The article argues that ways are needed of articulating what it is to experience disability in older age that are shared between older people's and disability sectors. It discusses bio-psychosocial models of disability as a means of doing so, one that avoids a return to an equation between older age and impairment, disability or decline. It concludes that more interrogation is needed of the separate philosophical underpinnings of disability and older people's sectors, argues for greater linkages between the two fields and for more exploration of social constructions of the experience of disability in later life.