The abbey was founded in 557 by Clotaire I on his manor of Crouy, near the villa of Syagrius, just outside the then boundaries of Soissons to house the remains of Saint Medard, the legend being that during the funeral procession the bier came to a standstill at Crouy and was impossible to move until the king had made a gift of the whole estate for the foundation of the abbey.
Besides Saint Medard, kings Clotaire I and Sigebert I were also buried here. In 751 Childeric III was deposed here, and Pippin the Short crowned. Richard Gerberding, the modern editor of Liber Historiae Francorum places its anonymous author here, ca 727.
Hilduin, abbot from 822 to 830, obtained in 826 from Pope Eugene II relics of Saint Sebastian and Saint Gregory the Great, and also succeeded in obtaining the transfer to the abbey of the relics of Saint Godehard and Saint Remigius. He rebuilt the church, which was consecrated on 27 August 841, in the presence of Charles the Bald and seventy-two prelates; the king himself assisted in carrying the body of Saint Medard into the new church.
In 833 Louis the Pious was imprisoned and underwent a public penance here.
The wealth of the abbey was immense. In the 12th century the community owned about two hundred and twenty fiefs. The abbey also minted coins.
Its wealth remained into the 16th century but the Wars of Religion ruined it, and although it was restored in 1637, it never regained its former stature. The abbey was dissolved in the French Revolution.
The buildings had disappeared by the beginning of the 20th century, except for the still extant but almost forgotten crypt of about 840.
The abbots of St. Medard's included: