It is bounded by (from the north and clockwise) the districts of Hanover, Peine, Wolfenbüttel, Goslar, Northeim, Holzminden and Hameln-Pyrmont.

The northern half of the district is highly urbanised, while the south is covered with forests.

The River Leine enters the district in the south, runs through the towns of Alfeld and Gronau and leaves in the northwest towards Hanover; a small affluent, the Innerste, joins the Leine from the east after flowing through the city of Hildesheim.

Between Leine and Innerste there are the forested hill chains of the Hildesheim Forest (Hildesheimer Wald) and the Sieben Berge ("Seven Hills", see Alfeld for more details).

The coat of arms displays: Media related to Landkreis Hildesheim at Wikimedia Commons