Tremaine church is probably the smallest parish church in Cornwall, being just twelve feet wide and forty-four feet long. Its charm lies in its unpretentious simplicity. The earliest parts of the church are Norman. The north wall and remains of the tympanum are Norman, while the south windows are square-headed sixteenth century. The tympanum apparently had a carved dragon, but was destroyed when a heating pipe was put in.

The two-stage un-buttressed tower is only thirty-one feet high and houses a single bell. The bell is inscribed with the words “Ave Maria Gracia Plena”.

The font with its simple band of cable carving is Norman. Arthur Mee in his guide to Cornwall inferred that it looks like a stone dumpling.

A strange feature are the small set of stone steps in the north wall, presumably originally leading to a rood loft, yet there hardly seems enough height to the building to afford such a feature.

The roof is a sixteenth century wagon roof with carved bosses.

There are good views from the churchyard, which in early summer boasts a large number of wild orchids. There are a number of interesting old gravestones of former parishioners.