Thermal properties of blends of poly(aryl ether ether ketone), PEEK, with a thermotropic liquid crystalline polymer, Vectra(R), were investigated by differential scanning calorimetry and X-ray diffraction techniques. Isothermal crystallization experiments were performed over a wide range of crystallization temperatures and compositions to follow the effect of Vectra(R) content on the crystallization kinetics of PEEK. A reduction in the crystallization rate of PEEK was related to a change in the mechanism of crystallization of PEEK, controlled in turn by the concentration of Vectra(R) in the blend. The addition of Vectra(R) resulted in a significant enhancement in the crystallization rate of PEEK. In addition, a reduction in this parameter is shown at a blend of 30% of Vectra(R). Differences in the crystallization behavior of PEEK are related to structural properties of these systems measured by simultaneous real time WAXS and SAXS experiments using synchrotron radiation. Results of melting behavior of PEEK, subsequent to isothermal crystallization, were interpreted based on the effects of Vectra(R) on the formation of two crystal families of PEEK. Melting temperatures of PEEK and crystallinity calculated from double endotherm are influenced by blending.