In this work, novel polypropylene/BiSr2CaCu2O6.5 (PP/Bi-1212) thick film composites having ceramic content varying between 0.5% and 6% were prepared to enhance both the dielectric and mechanical properties of PP. The surface morphologies of the samples were determined by scanning electron microscope. The crystallinity change in PP due to Bi-1212 filler was also described by differential scanning calorimetry analysis. The highest crystallinity degree was observed for the PP/0.5% Bi-1212 composite. The tensile parameters such as Young's modulus, tensile strength, percentage strain at break and energy at the break of the samples were also determined by analyzing the stress-strain curves. The highest tensile strength, stiffness, percentage strain at break and energy to break values were observed for the PP/(0.5%Bi-1212 composite. The complex electrical properties of the samples were also investigated by impedance spectroscopy measurements performed at room temperature between 10 Hz and 40 MHz frequency. The complex impedance, permittivity, ac conductivity and electrical modulus analyses revealed that 1% Bi-1212 additive changed the frequency dependence of the real and imaginary parts of the complex permittivity considerably and increased the dc conductivity of PP by approximately 0.2 million times. In this context, the percolation concentration for the conductivity of PP can be determined as approximately 1.0 wt% Bi-1212 filler. The electrical modulus analysis also indicated that the higher filler additive led the Maxwell-Wagner-type interfacial polarization in PP. Ultimately, it has been suggested that 3.0% of Bi-1212 added PP composite can be used as a dielectric material for decoupling capacitor applications.