The village is comparatively newer than those around it, as it started out in life as a castle belonging to the lord of the manor of nearby Hanslope. A settlement grew up around the castle of servants and manual workers, and this became the village of Castlethorpe (thorpe being the Old English word for a village). The castle was damaged in 1215 in a feud between Foulkes de Brent, who had been sent by the king, and William Mauduit, the castle's owner. Mauduit was reputedly in rebellion against King John of England. Although Mauduit returned to claim his seat after the king's death the castle was demolished shortly afterward.
The parish church is dedicated to St Simon and St Jude.