The municipality of San Juan is divided into 18 barrios, 16 of which fall within the former municipality of Río Piedras. Eight of the barrios are further divided into subbarrios, and they include the two barrios that originally composed the municipality of San Juan :

The barrios of Puerto Rico are the primary legal divisions of the seventy-eight municipalities of Puerto Rico. Puerto Rico's 78 municipios are divided into geographical sections called barrios and, as of 2010, there were 902 of them. In the US Census a barrio sometimes includes a division called a comunidad or subbarrio. In Puerto Rico, barrios are composed of sectors. The types of sectors (sectores) may vary, from normally sector to urbanización to reparto to barriada to residencial, among others.