This small chapel was originally part of the now-defunct Casa Grande de San Francisco, a huge Franciscan convent that was located until the 19th century in what is now Plaza Nueva and its adjoining areas. In fact, it can be considered that it is the only vestige that has reached our days of the disappeared convent.
On the outside, the chapel does not have a façade, since it was inserted in one of the buildings that surround Plaza Nueva. Inside, we see that it has a rectangular plan with a single nave, covered by a barrel vault with transverse arches and lunettes.
The main altarpiece was made by Bernardo Simón de Pineda around 1680 and the sculptures that appear in it have been linked to the workshop of Pedro Roldán. In the central niche appears an Immaculate Conception, flanked on both sides by San Fernando and San Hermenegildo.
The chapel has other altarpieces, among which the one dedicated to San Onofre stands out, at the beginning of the Gospel side, made at the beginning of the 17th century. Its sculptural part was made by the great Martínes Montañés, while Francisco Pacheco, Velázquez's father-in-law, was in charge of the paintings. The image of San Onofre is by Pedro Díaz de la Cueva from 1599.