The optimisation of process parameters in the electroplating process is imperative to improve the effectiveness of coating that meets the industry’s requirements. The present study analyses the influence of the electroplating parameters such as bath temperature, current intensity, and plating time on the hardness and corrosion properties of AZ31 Mg alloy. A preliminary electroplating coating was initially done on the AZ31 Mg alloy with zinc and copper. Subsequently, the AZ31 Mg alloy is coated with Ni-B4C composite by electroplating. Response Surface Methodology (RSM) is used to find the optimum settings for the parameters by minimising the corrosion loss and maximising the hardness. The quadratic regression models were developed for the responses based on the experiments conducted as per the Box-Behnken design method. Scanning Electron Microscopy (SEM), XRD analyses are used to investigate the effectiveness of the Ni–B4C composite coating on AZ31 Mg alloy. It is revealed from the results that the maximum hardness of 140 HV and minimum corrosion mass loss of 0.583 mg cm−2 was obtained for the optimal parameters.