The compositional dependent fracture behavior of soft PZT (Pb0.99Ba0.01(Zr1-xTix)(0.98)Nb0.02O3) ceramics in the vicinity of the morphotropic phase boundary was characterized using compact-tension specimens. The compositions with 0.40 <= x <= 0.55 displayed an increasing fracture resistance with crack extension (R-curve behavior). It was observed that the rhombohedral composition and the compositions near the morphotropic phase boundary showed the largest toughness enhancement. R-curve behavior was found to be influenced by the ferroelastic coercive stress, saturated remanent strain, and elastic modulus, which were experimentally measured for each composition. X-ray diffraction measurements were performed and compared to the fracture results to investigate the impact of phase and lattice distortion on ferroelastic toughening behavior.