After successfully leading a resistance to the siege of the Ostrogoth king, Totila, Justin was declared the first Catholic bishop of the city.

Construction of the present stone church was begun on October 28, 1628, based on designs by the architect Giovanni Coccapani, which were carried out by his pupil Ludovico Incontri.

The depiction seems odd, since the 16th century Jesuit missionary to India, Japan and China, appears to preach to an elegant crowd of Ancient Romans.

The painting of the Madonna delle Grazie (1451), by Neri di Bicci, originally in this church is now housed in the Diocesan Museum of Sacred Art in Volterra.

Gated inside the choir, the church contains an ancient altar, with a marble cover formerly over the tomb of St Justin, inscribed with the names of Cunincpert, 7th-century king of the Lombards, and the steward of the bishop Gaudenziano Alchis, founder of the first temple dedicated to San Giusto.