The present invention is directed to an improved method for metallizing polymer substrates, such as polyimides. The present invention comprises the steps of surface treating the polymer substrate with a plasma jet or corona discharge surface treatment, conditioning and etching the polymer substrate with an etching solution comprising a hydroxide and ionic palladium, activating the polymer substrate with ionic palladium, reducing the palladium on the polymer substrate, plating an electroless nickel layer onto the prepared polymer substrate, and plating an electroless copper layer over the electroless nickel layer. The process of the invention provides an improved method for preparing the polymer substrate for subsequent electrolytic plating thereon.