The Montfode Castle ruin lies close to Ardrossan, above the Montfode Braes (part of the raised beach), in the old Barony of Ardrossan. The castle ruins are clearly visible from the A78 Ardrossan bypass.The name 'Montfode' derives from the old Norman family of that name, the Montfodes of that Ilk. The Barony was originally held by the powerful De Morville family and the Montfodes would have been their vassals.

The castle was substantially demolished in the early 19th century to provide stone to the build a dam at Montfode Farm where the water was used to power a threshing machine. This dam and millpond no longer exists. Fortunately a drawing of the castle before it was robbed of stone for the dam construction. The remaining fragment of this baronial castle consists of a single round tower standing with slits and a gun-loop to around 8m, originally three or four storeys high and a portion of walling about 7m high and 2m long. The doorway on the eastern side has moulded stone surround the tower and wall are of rubble masonry. The position of this tower, situated upon an exterior angle, indicates that the building was of Z-plan.

Montfode Mount is a now oval and flat topped mound lies about 500m south of the castle, sitting on the edge of the Montfode Burn that has caused some erosion, and is often taken to be the site of the original Montfode motte. It is also seen as a burial mound, later becoming a fort, and later a court or moot hil. Indications of artificial scarping are visible and aerial photography has revealed signs of two circular ditches nearby and one around the base of the mound.The environmental remains from the site suggest a prehistoric date for all the features.

Boydston Farm was once known as Little Monfode, however local tradition relates that as a result of a feud one of the lairds of Montfode killed one of the Boyd family and in compensation gave the land to the Kilmarnock Boyds. The site of the murder was still well known in the 1860s, pointed out as the 'Cuff holm'.

A Norman family, the name Montfode has had many spellings, such as Monfode, Monfood, Munfode, Monfoit, Monfoid, etc. In 1417 Monfode de eodeum ('of that place') is recorded as being a member of a jury of fifteen who decided upon an action between the Royal Burgh of Irvine and William Frances of Stanecastle. In 1509 John Montfode is heir and acted as a witness in conjunction with William, Abbot of Kilwinning. In 1511 John Montfode, younger of that Ilk, together with Hugh, Earl of Eglinton, and several others acted together against John Scot, a Burgess of Irvine. They came to is house, assaulted his wife, striking her and pulling out much of he hair, taking the burgess to the tolbooth as a thief, imprisoning him for six hours, possibly at Montfode, and then putting him in the stocks.

In 1526 James Montfode was accused of taking part, together with the Earl of Eglinton and others, of murdering the Laird of Auchinharvie. James Montfode of that Ilk was killed at the Battle of Pinkie in 1547. A John Montfode is recorded in 1547 and in 1568 he was one of several Ayrshire barons who protested to the parliament in Edinburgh against the loss of their lands as a result of the Earl of Eglintons sentence for high treason as a result of his support of Mary Queen of Scots. Hugh succeeded him in 1600 and married Jean Boyd of the Portencross family.  Hugh Montfode had succeeded his father by 1621 and had three children, William, Margaret and Janet. William's heir was John Montfode of that Ilk, the last of the line. Margaret had died without any children and William was her heir.

The family became extinct in the 17th century, after five centuries of prominence in the locality. Janet Montfode married Archibald Steel in Corsmoor, Kilbride parish, being therefore the only line who can claim a link with the Montfodes. A Robert Craufurd in Montfode is recorded in 1621 as spouse to Margaret Lambie. Hugh Montfode of that Ilk's sister Jean was married to John Miller of Chapelton near Stewarton who died in 1622; they had a son Hugh Miller.

Montfode was held by the Earl of Eglinton briefly in 1661 before passing to William Brisbane by 1682, a druggist and surgeon in Ayr. William was Provost of Ayr in 1684 and was a leading advocate of the Presbyterian cause. Two people with the name Montfode appear as druggists in Ayr and some therefore employment arrangements may have been made with the former proprietors. William Ramsay, a commissioner of supply subsequently obtained the lands in 1714. Robert Carrick, a Glasgow banker, purchased the lands and in 1821 he was succeeded by James Moore, who took the name Carrick. Sir John Moore  of battle of Corunna fame was the brother of this James Carrick Moore.

A battle axe of grey stone was ploughed up in 1864 on top of Montfode Braes (name NS 224 439) near the remains of several ancient forts. It is of grey stone, with a small boss on either side. In 2002 an enclosure or cemetery was revealed at a previously unknown semi-circular enclosure with 60 cist and earth graves. The graves were concentrated in the SE of the site near an entrance in the enclosure ditch. A group of five buried storage tanks associated with the old Shell-Mex petrol refinery at Ardrossan were located just north of Montfode Castle. The whole depot area has been surrounded by a perimeter fence and their are several buildings surviving. The depot has a rail connection on the west side. Five connected fish trap boulder alignments having a combined length of some 200m are located at the mouth of the Montfode Burn. The boulders rest on the beach in association with rock outcrops.

William Montfode was recorded as being overseer to the children of Alexander of Cuninghame of Collellane in 1660.John Montfode, the last of that Olk, was a commissioner of supply and also was appointed to the commission of inquiry into the state of the Scottish church in 1662. Montfode Castle is said to be linked with Ardrossan Castle by a ley tunnel. A Chapelhill lies just to the east of Montfode Castle and a tumulus once sat on the crest of Knockrivoch Mount, again lying to the east.