Castelldefels is home to approximately 65,000 residents, making it a moderately sized city with a diverse population. The city attracts both local Catalans and international expats, particularly those who work in Barcelona but prefer to live in a quieter, coastal area. In recent years, the population has been growing due to its appeal as a residential area for families and professionals seeking a higher quality of life near the sea.
The demographics of Castelldefels include a mix of younger families, working professionals, and retirees, contributing to a dynamic community atmosphere. There is also a growing international community, with residents from various European countries, as well as Latin America and beyond.