A Saint Médard's church is mentioned in Clichy in the late 13th century. It was rebuilt in 1525 and restored from 1623 onwards by Saint-Vincent de Paul, the parish priest at that time. Work was completed on Maundy Thursday, 1630. The church is built on a Latin cross plan with a single nave and false vault. It has a stone tower built on a square plan, the front of which has a large blind window in the centre, with the main door to the building below it. The upper floor of the belfry has windows on either side with abat-sons. The tower roof is pyramid-shaped. The side walls of the nave are supported by buttresses, dividing them into 5 sections. Many repairs were undertaken during the 19th century.
In the old Saint Médard’s church, there is an ornate shrine containing the relics of Saint Vincent de Paul. There is also his ivory crucifix, the pulpit from which he used to preach and baptismal fonts. On the apse wall, in the choir, a white Carrara marble statue – the work of sculptor Alexandre Falguière – represents Vincent de Paul holding a child in his arms. This statue, made for the Pantheon in 1879, was moved to Clichy in 1943, initially temporarily but most probably indefinitely. To remedy the insufficient capacity of Saint Médard's, which had become too small due to the growing population, the apse was reduced to make room for a new church dedicated to Saint Vincent de Paul. Work by the architect Jacob Lequeux and contractor F. Souillart commenced in 1900. The two church buildings are interconnected, with Saint Vincent de Paul's running perpendicular to Saint Médard's. In neo-Roman style, Saint Vincent de Paul's church comprises a large nave with ribbed vaulting, supported by circular pillars forming the heart of the building, with an incomplete transept. Construction work was begun again in 1960, with a straight wall serving as a flat apse, while Saint Médard was separated by a straight wall after restoration.
Generous benefactors donated stained-glass windows depicting episodes of the life of Saint-Vincent de Paul in the side wings: planting a Judas tree, his meeting with Louise de Marillac, and the help he gave to the inhabitants of Gennevilliers. The high stained-glass windows commemorate Clichy's royal history, featuring several episodes from the life of King Dagobert.