Thermal rock properties were determined for the Northeast German Basin, a subbasin of the southern Permian basin in Europe. The new thermal data provide new aspects for the determination of heat flow and for hydrocarbon and geothermal resource evaluation in the basin. Thermal conductivity was measured on drill-core samples using the optical scanning method. Values for Permian and pre-Permian clastic rocks are variable (2.3–4.8 W/m/K) because of different depositional environments, compaction, and cementation reflected in lithology. Permian–Carboniferous igneous rocks show lowest thermal conductivity in basalts (2.2 W/m/K) and highest (3.1 W/m/K) in granitoids. Anisotropy of thermal conductivity in all rocks is low. Formation thermal conductivity was determined by upscaling the values determined for single lithotypes. Radiogenic heat production was determined on drill cores for the upper Paleozoic sediments and igneous rocks. For the younger formations without sample control, a well-log approach was used. The heat production of sedimentary rocks is lowest (0.4 W/m³) in the Permian (Zechstein) salt and anhydrite and highest (2.1 W/m³) in the Permian (Rotliegende) clastic rocks. Heat production of the Permian–Carboniferous rhyolites and granitoids is on the order of 2.6–3.8 W/m³, and heat production of andesites and basaltoids is on the order of 0.9–1.9 and 0.1–0.7 W/m³, respectively. The contribution to surface heat flow by these up to 2-km (1.2-mi)-thick igneous complexes amounts to 7 mW/m² at a maximum. On the same order is the total heat budget provided by the supra-Permian sedimentary succession in the basin.