Perfect absorber metamaterial (PAM) to reduce antenna radar cross section (RCS) is proposed. The novel low-RCS antenna is based on the concept of the PAM consisting of a periodic array of metallic dendritic structure and metallic square film etched on each face of a single substrate. The PAM processes high electromagnetic wave absorptivity for a wide incident angle. In the present letter, the PAM patterns are printed on the surface of a patch antenna to reduce the antenna RCS. It is demonstrated that, as compared to an antenna without the PAM, the proposed antenna RCS can be reduced drastically due to the fact that the PAM absorbs electromagnetic wave. Meanwhile, the proposed antenna can still maintain good radiation characteristics.