3D-nanoporous Pt (L2-ePt) films on multiarrayed microelectrodes electroplated from reverse micelle (L2) phase were evaluated in vitro for neural cell stimulation and extracellular potential recording. Impedance, capacitance, and charge injection limit were measured for the L2-ePt electrodes with various surface specific areas, i.e., roughness factors. L2-ePt with a roughness factor of 223 showed optimum performances as neural stimulation and recording electrodes, and its electric characteristics were electrode impedance of 0.039 Ω cm2 (1.17 kHz), electrode volume specific capacitance of 43 F cm−3 (1.17 kHz), and charge injection limit of 3 mC cm−2 (400 μs). L2-ePt showed higher mechanical strength than the conventional platinized Pt (Pt black).