Single-crystalline BaTiO3 nanocubes were synthesized by a hydrothermal method using a water-soluble titanium complex and surfactants. Ordered assemblies of BaTiO3 nanocubes were directly fabricated on substrates by the dip-coating method. To optimize the conjugation of the nanocubes, the sintering temperature was changed in the range of 750 to 900 °C to compare with the dielectric properties. The microstructures and dielectric properties of BaTiO3 nanocube assemblies sintered at various temperatures were characterized. The structure-property relation and the sintering temperature dependence of the dielectric properties are discussed. The assembly sintered at 850 °C showed the most enhanced dielectric properties. The face-to-face conjugation of the nanocubes was completed and there was good adhesion between the electrode and the assembly at 850 °C. The enhanced dielectric properties were considered to be due to the combination of the single-crystalline nanocubes and the interface between them.