Aside from being a unique temple, la Sagrada Família is in fact a functioning Roman Catholic church and mass is held every Sunday morning at 9 AM and Saturdays at 8 PM. The service lasts about 1 hour and it is performed in several languages to accommodate locals and tourists. The entrance is free of charge.
Space inside is limited, so entrance is on a first come and first served basis. If you wish to attend a service, you should be at the entrance close to the Nativity Facade before 8:30 AM for Sunday mass and 7:30 PM for Saturday service. There are some special dates for church services that take place throughout the year. It is essential that you dress and behave well when you attend mass.