This brief presents a wideband compensation method that addresses the hardware imperfections exhibited in an RF vector multiplier (RF-VM) used for RF predistortion systems. A wideband RF-VM model is first developed to embed the various sources of imperfections in an RF-VM. A compensation method is then presented, followed by a newly proposed identification algorithm to determine the parameters of the compensation modules. Experimental results indicated that the use of the proposed compensation method can lead to an improved error vector magnitude of up to 10 dB, when the RF-VM generates a synthesized predistortion signal of 150-MHz modulation bandwidth. Furthermore, an improvement up to 3.9 dB in the adjacent channel leakage ratio was obtained when using the compensated RF-VM to linearize solid-state power amplifiers driven by wideband communication signals.