Thousands of devotees from various parts of the country witnessed the holy event.
The Bishop of Thanjavur Dr M Devadass Ambrose presided over the flag hoisting ceremony.
After special prayers, the huge flag was taken in a procession around the church and hoisted later. Following this ceremony, holy mass, litany and benediction were conducted, church officials said.
During the festival days holy mass will be conducted at the main shrine and high mass in Tamil, Marathi, English, Konkani, Malayalam, Telugu and Hindi at the Basilica from morning till evening.
The most important event, 'Birthday of the Lady of Good Health' and Chariot Procession will take place on September 8.