This research paper deals with the synthesis of efficient and low cost heterogeneous catalyst from waste egg shells by wet impregnation method. A series of Zn doped CaO (0.5-2 wt% Zn2+ concentration in CaO) nano catalysts were prepared and employed in the transesterification of waste cooking oil. Synthesized catalysts were characterized by powder X-ray Diffraction (XRD), Fourier Transform-Infrared (FTIR), Scanning Electron Microscopy (SEM), Energy dispersive X-ray (EDX), and Transmission Electron Microscopy (TEM) analysis. Various reaction parameters such as Zn doping, catalyst loading, methanol: oil molar ratio and reaction time were optimized following Response Surface Methodology (RSM) based on Box-Behnken design (BBD). Maximum biodiesel conversion of 96.74% was recorded under the reaction conditions of 20:1 methanol to oil molar ratio, 5 wt% catalyst loading, 65 degrees C reaction temperature and 4 h of reaction time. The confirmation for biodiesel synthesis was performed using Proton Nuclear Magnetic Resonance (H-1 NMR) and Carbon Nuclear Magnetic Resonance (C-13 NMR) techniques. These results suggest that Zn doped CaO nanocatalyst is a promising catalyst for biodiesel production.