A new route for blending polyaniline (PAni) and EPDM rubber was devised with maleic anhydride as a compatibilizer precursor. Rubber matrices containing ammonium peroxidisulfate and dodecyl benzene sulfonic acid were cast from organic solvents. Exposure to the monomer vapors allowed the chemical polymerization of aniline. The influence of PAni and the compatibilizer on the thermal properties, chemical structure, electrical conductivity, and morphology of the mixtures was observed with differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared, in situ conductivity measurements, and optical microscopy. The micrographs showed a good distribution of the PAni complex in the matrix. The use of approximately 2 wt % compatibilizer resulted in chemical interactions between maleic anhydride and the PAni complex formed with dodecyl benzene sulfonic acid, which could enhance the compatibility between the polymers. The obtained blends reached relative electrical conductivity values of up to 9 x 10(-3) S cm(-1).