To identify the main conditioning factors that Primary Care professionals indicate when implementing and developing interventions on isolation and loneliness. Qualitative research with grounded theory, systematic analysis and narrative design of topics. Developed in 12 Primary Care centres of the Health District of Córdoba and Guadalquivir, covering urban and rural areas. Three profiles were identified: family medicine/community care, community nursing and case management nursing. The selection was carried out among those who showed greater motivation and commitment to an intervention on isolation/loneliness. Purposive sampling. The work was based on individual in-depth interviews, focus groups and dialogic interviews. (a) Distorted images persist about loneliness/social isolation and living alone that make it challenging to identify; (b) the main disruptive determinants in the structure and organization of the care system have to do with the absence of screening programs, the hegemony of the biomedical model and the deficit of resources (in light of this model); (c) the main facilitators are linked to the nursing role, privileged for these interventions according to the participants; and, finally, (d) personal components are necessary, both from the older adult and from the professionals. Intervention on social isolation and loneliness in Primary Care is conditioned by organizational and structural, professional and personal factors. It is essential to take them into account in order to guarantee their feasibility.