This work completes our recent research on conductive PVDF/PET based blends designed for Proton Exchange Membrane Fuel Cell bipolar plates. We focused on isothermal crystallization kinetics of these conductive blends by using the logarithmic form of the Avrami equation. The samples were quickly heated up to 280oC at a heating rate of 200oC/min and held at this temperature for 10 min, to eliminate the thermal history. Then, they were rapidly cooled at -200oC/min to the desired crystallization temperature, Tc, and then held at this temperature for 20 min. The studied pre-crystallization temperatures were 190 and 180oC at which the PET phase could crystallize where the PVDF phase still in the melted state. This enabled us to elucidate the influence of PET phase pre-crystallization on the crystallization of PVDF phase at four temperatures: 138, 140, 142 and 144oC. It was observed that, for PVDF/PET based blends without PET pre-crystallization or with PET pre-crystallization at 190oC (PET190) and 180oC (PET180), many PET crystals were developed inside the PET phase before the PVDF phase began to crystallize. The fact that the Avrami exponent still between 2 and 3 was an indication that PET crystallization didn’t change the nucleation and growth mechanisms of PVDF spherulites. This was mainly due to the fact that the PVDF phase was the matrix phase and PVDF macromolecular chains were not significantly restricted in motion by the PET phase. At the same crystallization temperature (Tc= 138, 140, 142, or 144oC), it was observed that the crystallization rate, G, for the whole blend presented the following behavior: G (PET190) ＞ G (PET180). It is clear that a more crystalline matrix phase presents higher volume shrinking and consequently releases more space for PVDF to crystallize. So PVDF crystallization is accelerated with increasing the treatment temperature.