This is a church belonging to late Gothic, from the early sixteenth century. A later addition would be the doorway of the south façade. It is currently still the parish church of Arnuero, and its visit is included in the visit to the Art Observatory of the Ecoparque de Trasmiera.
It is a rectangular-plan church, with a large nave divided into three bays and ending in a square apse. In the crossing there are side chapels, and on the gable end there is a square tower rising, sheltering the entrance door.
Its late Gothic style is characteristic of an entire series of churches in the coastal region of Cantabria, especially in Trasmiera. All of them share similar features, among which the flamboyant-style porch stands out. In this regard, mention may be made of the churches of Castillo Siete Villas, Heras, Matienzo, Omoño, Pámanes or Valdecilla. In this church of Arnuero, the late Gothic doorway is on the western wall, beneath the tower. It is chamfered, with a carpanel arch above which runs a vegetal frieze and several archivolts decorated with besantes. The cut-roll in a pointed arch shape displays vegetal motifs in the soffit. A finial appears at the vertex, as a crowning, and on either side decorative buttresses rise, topped with pinnacles. Today, another door is used more, which is on the south façade, and since it is already fully Renaissance, it dates from the mid-sixteenth century.
As for the interior, it is spacious and open. The walls are made of rubble stone. The nave is covered by rib vaults, with tiercerons and curved ribs. The only monumental sculpture is the capitals, carved in low relief with vegetal motifs. More prominent is the freestanding sculpture, in particular the notable high altarpiece, in Plateresque style—one of the most outstanding in Cantabria. Attributed to Simón de Bueras, it was executed between 1540 and 1542. It contains scenes from the Life of Jesus and of Mary.
It was declared an Asset of Cultural Interest in 1993, in the category of monument. The high altarpiece is also listed as a movable Asset of Cultural Interest.