Derman-Ostroh National Nature Park sits in a river valley that separates the southern edge of the Polesian Lowland, and the northern edge of the Podolian Upland in northwestern Ukraine. The terrain is a mixture of pine-oak forest and marshy river lowlands. The park is in the administrative districts of Zdolbuniv Raion and Ostroh Raion, in the southernmost region of Rivne Oblast.