Boron-doped diamond powder (BDDP) was prepared using various sizes of diamond powder (DP) core (300-2600 nm), and the electrochemical properties of a screen-printed electrode obtained using the BDDP ink were investigated. The use of larger DP cores led to faster growth rate of the BDD layer on the DP core surface and lower sp(2) carbon impurities content. Screen-printed electrodes prepared using large BDDPs showed wide potential window, low background current, and good electrochemical response, including direct oxidation of bovine serum albumin.