The Chapel of the Third Order is just outside the Xochimilco Cathedral and on the same ground. A single nave is fronted by a façade of four bodies built in the 18th century. The Third Order Congregation was well established by the end of the 17th century. The Third Order were a group of Spanish-born lay-Franciscans, especially dedicated to following in the footsteps of Saint Francis of Assisi. (The First Order were clergy, and the Second Order, the sisterhood of Nuns.) Their patron saint here though was Saint Louis, King of France.
They began building their chapel here at the beginning of the 18th century. A chapel on the same spot had served as a tabernacle for the Cathedral in prior years.
Many of the early and most prominent members of the congregation were interred within this church. By the mid-20th-century, the Secretary of Education installed a library within the chapel to support the primary schools still working in the monastery. This was never completed and the congregation decided to return the chapel to control of the Cathedral. In 1951, it was return but in a very diminished state. A major reconstruction began and this lasted until 1953. The Mexican government recognized the Chapel of the Third Order as a historical monument in 1932.