Municipal registry data as of January 1, 2026, shows a total population of 1,729,963 inhabitants, a slight decrease compared to the previous year. Seven of Barcelona's ten districts have experienced population losses, while Ciutat Vella, Nou Barris, and Sant Andreu have seen minor increases. Deputy Mayor Jordi Valls attributed this decline to administrative corrections in the registry, noting that Barcelona continues to be an "entry point" to the region.

The population drop would be much more significant without immigration, as the natural growth rate is negative. Birth rates have hit historic lows, with 11,012 births in 2025, the lowest figure since 1900, with the exception of 1939. The difference between births and deaths (14,557) results in a negative balance of 3,549 people. Only Ciutat Vella, with 54.8% foreign population, manages more births than deaths.

Aging is a clear trend, with the average age rising to 44.6 years and a record 1,196 centenarians, predominantly women. Concurrently, a youth exodus is observed: many young Spaniards are leaving the Catalan capital, mainly for other municipalities in Catalonia (68.4%) and the rest of Spain (23.7%), often due to the housing crisis. This has led to an increase in single-person households, which now exceed 218,000.

Migration is consolidating as the city's primary demographic driver. 81.6% of new registrants are young adults born abroad, and 44% of them hold university degrees, raising the overall academic level. The population born in Barcelona now represents 44.6%, while those born abroad total 626,924 (36.2%), with a majority originating from the Americas. The city hosts 182 different nationalities.