Electronics assemblies incorporating three-dimensional heat flow structures are disclosed herein. In one embodiment, an electronics assembly includes a substrate having a surface defining a plane, a heat generating component coupled to the surface of the substrate, a cooling device positioned outside of the plane defined by the surface of the substrate, and a three-dimensional heat flow structure. The three-dimensional heat flow structure includes a first portion thermally coupled to the heat generating component and a second portion extending from the first portion. At least a portion of the first portion is parallel to the plane defined by the substrate. The second portion is transverse to the plane defined by the surface of the substrate. The second portion is thermally coupled to the cooling device such that the three-dimensional heat flow structure thermally couples the heat generating component to the cooling device.