Palladium composite membranes obtained by supporting thin palladium films on ceramic substrates have good thermal and mechanical stability and a high hydrogen permeation flux due to the reduced palladium film thickness. The key factor in applications of these composite membranes for hydrogen separation and in membrane catalysis is their hydrogen selectivity. In this paper, a Pd/alpha-Al2O3 composite membrane with a large number of defects was prepared initially using the conventional electroless plating technique. Subsequently, these defects were repaired using the electroless plating combined osmosis technique. All defects disappeared and no nitrogen leak through the membrane was observed at room temperature. It was found that after repair the hydrogen selectivity of the composite membrane was increased considerably without reduction of its hydrogen permeation flux or significant increase in the palladium thickness.