In utero electroporation is a powerful tool to transfect and manipulate neural-precursor cells of the rodent parietal cortex and their progeny in vivo. Although this technique can potentially target numerous brain areas, reliability of transfection in some brain regions is low or physical access is limited. Here we present a new in utero electroporation configuration based on the use of three electrodes, the relative position and polarities of which can be adjusted. The technique allows easy access and exceedingly reliable monolateral or bilateral transfection at brain locations that could only be sporadically targeted before. By improvement in the efficiency of the electrical field distribution, demonstrated here by a mathematical simulation, the multi-electrode configuration also extends the developmental timeframe for reliable in utero electroporation, allowing for the first time specific transfection of Purkinje cells in the rat cerebellum.