One of the most important elements of a traditional Quinceañera is the Mass of Thanksgiving (Misa de Acción de Grácias). The purpose of the Mass is to give thanks to the Quince girl's family and friends and also to formally present the Quince as an adult member of society.

Traditionally, the mass begins with a procession down the aisle. The Quince is escorted by her parents or godparents and her Court of Honor follow. There are traditional aspects of the mass that some Quinces choose to include in their ceremony. For example, sometimes, the Quince carries her "Last Doll" a token bestowed upon her by an aunt or other female relative. At the altar, the doll is exchanged for a bouquet of flowers, symbolizing the Quince's leaving childhood and entering a new stage in her life. Some Quinces choose to include the Last Doll tradition during the celebration after the mass; and some forgo it altogether.

Another traditional part of the mass is the Crowning, in which the Quince is stripped of the headpiece she wore into the church and is crowned by her mother and/or godmother with a beautiful tiara. This, too, symbolizes the Quince’s transition from childhood to adulthood. Also, during the mass, the Quince is presented with a Bible and a rosary, which symbolize her new role in and commitment to the church. Again, some modern Quinceañeras include this as part of the celebration after the mass.

There is no right or wrong way to celebrate the Mass of Thanksgiving. Most girls choose to have one and consider it to be an important part of their Quinceañera, although some choose not to have a mass and opt solely for a giant celebration with their friends and family. Some Quinces choose to incorporate a few traditional elements and not others. There are even some non-Catholic Quinces who are starting new traditions. Just remember, if you have a Quinceañera mass, make sure it is a reflection of who you are.