In Spain, the public National Health Service provides care to Spaniards and other residents and is tailored for a decentralized state of autonomies. Each Autonomous Community has legislative capacity in its organization and management. We study the case of the collaboration between private hospitals and the public health service in La Rioja, an Autonomous Community of Spain located in the North of the Iberian Peninsula, due to the importance that this relationship has in health systems, in general. We applied the case study method as a methodological tool in a long-term local study. The interpretation was carried out within a national context, which allows us to understand its meaning and the historical keys to hospital development in this region. Primary sources have been reviewed (mainly reports, catalogs, and censuses of hospitals from the Ministry of Health and the Government of La Rioja) and other secondary sources, located in archives, libraries, Institute of Rioja Studies, and Department of Health. The hospital system in La Rioja was characterized by a predominance of public beds compared with private ones, although there has been a growing trend in the number of private beds from 2013 onwards due to the incorporation of health and social care convalescent hospitals (two). La Rioja has been promoting public–private collaboration (seen as a strategic alliance) and focusing on agreements in the socio-health space, particularly using the management service agreement and the concession of work formulas. The development of the public health service in La Rioja, from 1986 to 2019, has been determined by a progressive lower dependence on specialized hospitals from other health services of neighboring Autonomous Communities and by a mixed public–private hospital system.