Diamond-based microelectrode arrays were fabricated by using nanocrystalline diamond as an insulating layer and conductive boron-doped in order to used them for analysis of brain cortical slices. MEA surface is solely composed of diamond, exposed to the cells. The impedance measurements showed negligible cross-talk between neighbouring diamond microelectrodes. Local field potentials related to neural signals were then successfully recorded from pharmacologically disinhibited rat cortical tissue slices, mechanically coupled on the surface of the MEA. The background signal level of the diamond MEAs was found to be lower than commercial Pt-based MEAs, under identical measurement conditions.