The "Pieve di Santa Maria Assunta" was a pieve matrice that oversaw a well-defined territory in its dimensions, the so-called piviere. 

The pieve matrice was the only one within the jurisdiction that possessed the baptismal font (the only one to administer baptism), the cemetery, and a permanent priest, upon whom other ecclesiastics depended who officiated the chapels erected in the surrounding villages and within the territory.

The first historical document in which the pieve of Fagagna appears dates back to 1247 and lists the pievi within the church of Aquileia and the related taxation. Fagagna was the first for tax imposition, thus confirming its importance and wealth. In 1250, due to the betrayal of Rizzardo, pievano of Fagagna, and Mainardo, provost of San Pietro in Cargna, the pieve of Fagagna was granted to the chapter of Cividale. From then on, the pieve was spiritually governed by the chapter through two of its vicars who were chosen by the Community of Fagagna (giuspatronato). The church of S. Maria Assunta was reserved the right to also appoint the cameraro of the church (administrator of goods and rents). 

It is a vast building with a recently restored (1983) gabled facade. The interior, a baptismal font with three naves, preserves the altar built at the beginning of the 18th century and ennobled by four statues. The baptismal font is interesting, signed and dated 1504 by the most renowned of the Lombard stonemasons working in Friuli: Giovanni Antonio Pilacorte. Majestic in style, it features a bas-relief with the Baptism of Christ on the dado, foliage decoration on the shaft, and a bowl with a beautiful floral motif and typical Lombard Renaissance carving decorations.