The phase transition behavior of the pseudobinary (1-x)Pb(Yb1/2Nb1/2) O-3-xPb(Fe1/2Nb1/2)O-3 [PYN-PFN] system has been investigated by X-ray diffraction and dielectric measurements. As the PFN content increases, the transition behavior changes from paraelectric-antiferroelectric to typical relaxer via the relaxer to normal. The relaxer to normal transition of the system is characterized by a normal state of antiferroelectric and is thought to arise from structural variation due to the local disorder of B-site ions.