In 1994, the mayor of Conteville in Normandy, André Dubreuil, noted that during land rehabilitation of the old quarry of Pierre de Caen, dinosaur bones had surfaced.

However, professional excavations only started in 1998 when the rock of the collapsed quarry face had already been spread by a bulldozer over a considerable surface.

It proved necessary to dig up and sieve many cubic metres of rubble over several years, ultimately salvaging about two thousand bone fragments, varying in size between one and ten centimetres.

The specific name referred to the nearby ancient battlefield of the Battle of Val-ès-Dunes, where William the Conqueror had in 1046 defeated his enemies.

[3] The holotype, MNHN 1998-13, has been uncovered in a layer of the Calcaire de Caen dating from the middle Bathonian.

Preserved parts include: the majority of the skull; the splenial and angular of the lower jaw, a natural mold of the surangular, two cervical vertebrae, cervical ribs, seven dorsals, ribs, gastralia, three sacrals, ten caudals, a chevron, a piece of the scapula, a claw of the hand, a partial thighbone, the upper part of a shinbone, a partial fibula, a fifth metatarsal and the first phalanx of the third toe.

The holotype was an individual by Gregory S. Paul estimated to measure 5 metres (16 ft) long and to weigh 250 kilograms (550 lb).

[3] In 2012 Matthew Carrano added one autapomorphy: on the rear of the braincase there is a notch between the basioccipital and the bone surface formed by the exoccipitals and the opisthotic.

[5] Dubreuillosaurus seemed to lack any sort of crest or horns, but the only known specimen is a juvenile, and it is possible that these structures developed in later life.

The fossil of Dubreuillosaurus was discovered in sedimentary rocks that were laid down in coastal, mangrove swamps at the east coast of the Armorican Massif.

[2] Though uncovered at an island Dubreuillosaurus did not show the effects of insular dwarfism; like with Eustreptospondylus its small size is due to its being a subadult.