Electrostatic plugging is used to improve plasma confinement in a multidipole ion source. A conventional multidipole device is modified by placing positively biased electrodes on both sides of each magnetic line cusp. As the electrode bias voltage is increased from zero, plasma density increases by approximately a factor of 2 and the plasma potential follows the electrode potential. The density enhancement is reduced as neutral pressure is increased or if the electrode‐gap width is decreased. Similar behavior is observed when a negatively biased grid is present. A model which assumes that the main electron‐loss mechanism at high electrode bias is diffusion across the cusp magnetic field lines is shown to be in qualitative agreement with measurements.