The village of La Garde-Adhémar has preserved its medieval structure within the ramparts bordering the rocky outcrop that dominates the Pierrelatte plain. This plain was colonized during the Roman era by veterans of the Roman legions (1st Century AD). Recent archeological research have revealed numerous traces of human habitation, linked in part to the wine-growing industry. Via Agrippa passed at the foot of La Garde. Traces of Gallo-Roman settlements have been located in the hills. The site of Val des Nymphes ("Valley of the Nymphs"), 2 kilometers from the present location of the perched village, bears witness to the worship of water gods and mother goddesses. A small altar, dedicated to the Nymph goddesses, was found close by and was moved in front of the entrance of the Saint-Michel church
	The last archeological and historical digs have detected, close to the permanent spring of Val des Nymphes, the presence of an important medieval settlement (Vth - XIIth centuries) and four churches. Today, there only remains a prioral church that was built in the XIIth century by the monks of the abbey of Tournus, in Burgundy (first mentioned in 1059). It should be the original site of the village. Beginning at the end of the XIIth century, this site was progressively abandoned by the inhabitants who favored instead the living conditions in the fortified village of Garde-Adhémar whose Lords, for a long time, belonged to the Adhémar family. In the XIIth century, the Saint-Michel church also dependent on the Abbey of Tournus, was built in an elegant Romanesque Provencal style.
		For centuries, the pace of village life was dependent upon agriculture and crafts. In the XVIth century, Antoine Escalin, also called "Le Poulin"("The foal"), Ambassador, Commander in Chief of the Royal Galleys and Lord of the country, built a magnificent Renaissance castle that was demolished after 1810.
		In the XIXth Century, the farms got closer to the farmlands and multiplied in the plain and hills. Rural exodus accelerates the decline of this perched village that partly falls in ruins. In one century, the commune goes from 1,260 inhabitants in 1860 to 504 in 1954. Since then, the development of the nuclear power plant of Tricastin has attracted a new population, thereby the renovation of old homes and the development of new housing estates. The population is now stable with 1,077 inhabitants in 1982, 1,075 in 1999.