The construction of a brick church in Kościelna Jania is attributed to the Teutonic Order around 1355. Until the sixteenth century, the church performed under the invocation of Saint Nicholas, patron of merchants and sailors. Around 1538, the nave of the church was destroyed, which was first rebuilt from wood. It was not until 1622 that a new brick corpus was erected at the initiative of Jan Kostka.
It is not known what the original nave of the medieval church looked like. If the later, early modern structure was erected on the foundations of an older one, it was an aisleless structure without a chancel separated externally, perhaps closed polygonally in the east. On the west side, the church had a massive four-storey tower, reinforced in the corners with high, stepped buttresses. Its elevations are decorated with long, pointed blendes, in which small window openings have been pierced. In the ground floor of the west facade, a pointed, stepped, moulded entrance portal was created.
From the original medieval church, a huge, buttressed, four-storey defensive tower has survived. Inside the church, one can see a 14th-century Gothic font, carved out of stone.