The building stands near the 17th century Santi Giovanni and Carlo al Fopponino church. Ponti included this old building in his project and connected it with the new parish structure through a walkway. The basement houses a movie theater, meeting rooms and rooms for the catechism. The access to the church is raised from the road level, to which it is connected by a sloping parvis and a central stairway.

The façade is a connecting element between the church and the surrounding buildings and consist of a sloping blind wall perforated by openings framing the sky. This special treatment creates plays of light and shade and contrasting effects, which were later used by the architect in other works. The entrance is in the center of the façade: a door with three arches and triangular gables. The simple decoration of the façade includes symbols linked to Franciscan preaching, like the tau-shaped crosses, obtained by laying some flat ceramic tiles among the iridescent diamond-shaped tiles covering the whole building. Also the external pulpit hints at the figure of San Francesco.
Inside, the hexagon-plan church is simple and essential, consistent with the designer’s opinion on sacred architecture. The naves and two aisles are divided by tapered pillars and reinforced concrete beams. Light plays a very important role: it comes in through diamond-shaped hexagonal openings and splayed quadrangular windows, and is filtered by reinforced concrete screens inspired by Le Corbusier’s architecture.

The building is traditionally and symbolically oriented towards east. Ponti also designed liturgical furniture, church furnishings and liturgical vestments. The High Altar echoes the diamond shape used elsewhere in the building. The architect also designed the decoration and artistic aspects of the church. The cycle dedicated to the life of San Francesco, painted by Francesco Tabusso, is on the side walls. The large apsidal altarpiece dedicated to the Canticle of the Sun is another work by the same painter. The wooden crucifix that stands in the apse and the mahogany statue representing the Virgin Mary holding Jesus in her arms are by Don Marco Melzi.

The glass wall on the façade, particularly complex because of its diamond-like 3-D shape, and the side windows are the work of Cristoforo De Amicis.

The following works were added at a later time: a crucifix by Francesco Tomea, two bronze statues (San Francesco d'Assisi and Sant'Antonio Abate) by Virginio Ciminaghi, a bronze statue (Santa Madre Chiesa) by Alessandro Anastasio and a painting by Giuseppe Ingegnoli (Cristo Consacrante).