Personal Assistance, a service aimed at facilitating the development of the life project of people with care needs and in which they decide how and when to be supported, has been scarcely developed since its inclusion in Spanish care policy in 2006. The pilot projects A Gusto en Mi Casa and INTecum, promoted by the Junta de Castilla y León to test new models of long-term and end-of-life care, both based on comprehensive, community-integrated, and person-centered care, incorporated the Personal Assistance Service as a cornerstone. This paper analyzes the evidence from the evaluation processes of both projects to identify the service’s contributions to the social sustainability of the care system in Castilla y León and its limitations. Based on 257 surveys, 105 interviews, and nine focus groups, this study concludes that the Personal Assistance Service aspires to be a key element in the social sustainability of Castilla y León’s care system, resulting in high levels of satisfaction among beneficiaries, families, and professionals. However, the service faces challenges such as the lack of clarity about the tasks of Personal Assistants, difficulties in recruiting and training professionals, and the need to implement measures to address gender inequalities in care provision.