The powder metallurgical techniques capable of powder mass production but lacks in achieving high zT. Therefore, to improve zT, electroless surface coating was performed on water atomized Bi0.5Sb1.5Te3 (BST) powder and stimulated their conducting nature. Surface chemical composition studies displays fine elemental coating on the BST powders and remarkably, the Seebeck coefficient increased till 450 K. The surface coated bulk sample shows greatly improved power factor about ~45% higher than uncoated sample. Indeed, at high tem-perature we obtained reduced lattice thermal conductivity which confirms the remarkable suppression of bipolarthermal conductivity. Consequently, a maximum zT of 1.16 at 400 K achieved by coated samples which is ~102% enhancement compared to original BST. Also, we attained high average zT of ~0.99 which helps in employing thermoelectric devices across wide temperature. Therefore, electroless surface coating could be a feasible method for improving the properties of mass-produced BST powder.