Small amounts of Cu and Al-K substitution on the A and B site of BaTiO3, respectively resulting a solid solution of the type Ba1-xCuxTi1-x(AlK)xO3 (BCTAK) [x = 0.05, 0.10, 0.15, 0.20] have been investigated. The compositions have been prepared in the nanocrystalline range by chemical route. X-ray diffraction revealed the tetragonal (P4/mmm) phase. Average crystallite size and particle size were found to be in the range between 25 nm and 35 nm which were analyzed through X-ray diffraction and transmission electron microscopy respectively. A dielectric study of these compounds as a function of temperature suggested that with increasing substitution concentration the dielectric constant decreased and the Curie temperature shifted towards the lower temperature side. Discontinuous grain growth accompanied with excellent dielectric diffuseness was found with increasing concentration of substitution. The dielectric diffuseness γ was found to be maximum to 1.91 at the substitution of BCTAK x = 0.20. The activation energy, Ea was found to decrease along with an increase in conductivity with increasing substitution concentration in BCTAK.