The church dedicated to Saint Leopold was built between 1903 and 1907 by the 63-year-old architect Otto Wagner, with mosaics and stained glass by Koloman Moser, and sculptural angels by Othmar Schimkowitz (1864–1947).

Otto Wagner incorporated numerous features specifically related to its function within an asylum: e.g. there are very few sharp edges, and most corners are rounded; almost no crosses are visible; the priest's area is potentially entirely separate from the patients'; access to the pulpit is only from the vestry; emergency exits are built into the side walls in case a patient needed to be speedily removed; continuously flowing water replaced holy water stoups at the entrance; there were separate entrances for male and female patients, since gender segregation was mandatory in mental institutions at the time; confessionals were more open than is customary.

The central ceiling below the unseen dome bears images relating to the four evangelists: the man for Matthew, the lion for Mark, the calf for Luke, the eagle for John.

The magnificent windows at the sides of the Kirche am Steinhof portray seven saints (named underneath each frame) fulfilling Christ's commands both temporal (feed the hungry, clothe the naked, etc.)

Due to lack of funds, several of Otto Wagner's original designs were never realized, including the Procession of the Cross, a private chapel beneath the church for Protestant services, and a Jewish synagogue.

In an article published in the New Free Press on October 6, 1907, the author rhetorically asked: "And is it not a beautiful irony of fate, that the first sensible secessionist building in Vienna has been built for the insane?"

Between 2002 and 2004, the entirety of the church's 1,800m² façade was replaced with 3000 plates of Carrara marble, each tile having been examined by ultrasound to ensure quality.

The mosaics within the church, main altar, pulpit, chandeliers, sconces, and wall decorations were restored and newly gilded.

While the interior renovations were ongoing, the foundation of the church, the drainage system, and the exterior base were completely renewed.