Besides the town of Dillingen proper, the municipality encompasses the villages of Donaualtheim, Fristingen, Hausen, Kicklingen, Schretzheim and Steinheim.
Schretzheim is notable for its 6th to 7th century Alemannic cemetery, 630 row graves in an area of 100 by 140 metres. The counts of Dillingen ruled from the 10th to the 13th century; in 1258 the territory was turned over to the Prince Bishops of Augsburg. After the Reformation, the Bishops of Augsburg moved to the Catholic city of Dillingen and made it one of the centers of the Counter-Reformation.
A university was established in 1549, but was closed by Napoleon in 1804. The philosophical and theological faculties still existed in the 20th century. In 1971, however, it became a part of the Bavarian Center for the Education and Training of Teachers and Personnel Management (Akademie für Lehrerfortbildung und Personalführung). One of the largest employers in the city is Bosch and Siemens Household Appliances, producer of household applicances.
In ancient times the Danube river was a border between the Roman empire and the Germanic tribes north of the river. The Roman camp of Phoebiana (now Faimingen) was a bridgehead crossing the danube. There was an Apollo temple being one of the largest buildings north of the Alps in that time.
In medieval times the county of Dillingen was established. The counts of Dillingen ruled from the 10th to the 13th century, then (1258) the territory was turned over to the Prince Bishops of Augsburg, who gained several villages for their clerical state, hence subdividing the region into several patches, which were dissolved in the early 19th century. In 1804 Dillingen and its area became part of the state of Bavaria.
The district was established in 1972 by merging the former district of Dillingen (which had existed since 1804) with the western half of the former district of Wertingen. The city of Dillingen lost its status as a district-free city and became the capital of the newly established district.