The settlement of Banchory-Ternan, or Banchory as it is known today, began to grow in the fifth to sixth century AD when a Christian College was founded by St Ternan on the banks of the River Dee close to the present day graveyard. St Ternan was a pict who converted to Christianity and travelled Europe before founding the college or "Banchor". Here he taught both religion and the latest farming techniques learnt on his travels. Remains of Celtic foundations can be seen in a number of carved stones close by the old graveyard.
The importance of the college can be gauged by the number of saints who have a connection with the area - St Machar; St Arnaud; St Duthac; St Nathalan; St Erchard; St Nidan; St Devenick and St Congol.
The relics were lost after the Reformation but were recorded as being St Ternan's bell (ronnecht), his copy of the gospels kept in a gold and silver box (cumdach) and his scalp or tonsure where he would have been anointed and blessed as a missionary. A bell, discovered when the Deeside Railway was being constructed in the nineteenth century in the Bellfield park, is thought to be similar to a Saint's bell or "Ronnecht" and can be seen in the East Church.
On the 12th of June each year a Fair was held in the Saint's honour. This was particularly popular in medieval times as it was one of the few holidays that workers enjoyed. They paraded St Ternan's relics around the church. The market cross, which originally stood on the site of the annual fairground, now stands in the grounds of the East Church. Banchory continues to hold St Ternan's Fair in early June each year to commemorate St Ternan.
In the medieval period there were many struggles between local warlords who operated from the tower houses located on river banks at Strachan, Tilquhilie, Durris, Cluny-Crighton and Banchory. The area also found itself in the midst of national battles including Macbeth at Lumphanan and Mary Queen of Scots at Corrichie.