The Church of Saint-Jacques is Dieppe's most important medieval building, a Gothic structure that was begun in the twelfth century and expanded over the following four hundred years. The result is a building with clearly different architectural periods visible in its proportions — the tower, the nave, and the choir all show their separate eras. The exterior stonework is worn by centuries of Channel weather but still detailed.
The interior is spacious and relatively uncluttered. The carved decorations are the main attraction, including some well-preserved sixteenth-century work that reflects Dieppe's position as a major port in the age of exploration. The church sits in the heart of the old town, surrounded by streets that still have the proportions and some of the buildings of their medieval origins. Mass is still celebrated regularly; the building is open to visitors outside service times.