In this paper, a planar nine-way metamaterial power-combined amplifier implemented with microstrip grids, lumped capacitors and inductors, and power amplifiers is presented. The power-dividing/combining structure is a metamaterial lens composed of positive refractive index (PRI) material with right-handed unit cells and zero refractive index (ZRI) material with left-handed unit cells. A semi-circular interface is between PRI and ZRI materials. The infinite wavelength phenomenon in the ZRI material attains an equal magnitude and phase distribution to have an interconnection with the collinearly aligned amplifiers as a nine-way metamaterial power-combined amplifier with its input and output ports at the two focal points of a planar PRI–ZRI–PRI lens. An output power of 7.64 W with a combining efficiency of 85% is measured at 1.008 GHz. Through the field measurement to each unit cell, the dividing/combining phenomenon is experimentally verified and shown in a good agreement with simulation results. Furthermore, the graceful degradation characteristic of this power-combined amplifier is experimentally demonstrated.