In this paper metallization of a liquid crystal polymer (LCP) substrate by physical vapor deposition (PVD) is described. Pretreatment of LCP substrates with oxygen-containing plasma improves the adhesion strength between the PVD copper layer and Substrate. When a nickel interlayer was used, the adhesion was improved further. Still higher adhesion was also achieved with appropriate bias used during deposition of the nickel interlayer by PVD. Even after 1000 cycles of thermal shock the adhesion strength of Cu/Ni on LCP pretreated with oxygen plasma was still high.