This paper reports on the controlled synthesis of 3D CuO nanogrids by the combined use of electrospinning and thermal oxidation of a composite metal mesh/polymer mat architecture. The obtained nanogrids result from three steps encompassing: (i) Cu atom clusters diffusing into the nanofibers producing polymer-metal "core-shell"-type fibers (ii) decomposition of the polymeric shell; (iii) oxidation of the metallic core of the nanofibers to form self-supported, open nanogrids consisting of continuous nanofibers of CuO nanoparticles with an average diameter of 20 nm. The calculated band gap energy of the cupric oxide nanogrids was determined from the UV-Vis spectrum to be 1.32 eV. The unique 3D CuO nanogrids may be used as key components of 3D nanobatteries, photocatalysts, and p-type chemosensors.