Polyaniline (PANI)/activated carbon (AC) composites are prepared by in situ emulsion polymerization using dodecyl benzenesulfonic acid (DBSA). DBSA can play a role as both surfactant and dopant in the process of PANI synthesis. The effect of DBSA on the preparation of PANI/AC composites is investigated in this research. For this purpose, the composites are prepared in micellar solutions with various concentrations of DBSA. It is confirmed using X-ray diffraction (XRD) analysis and Fourier-transform IR (FT-IR) spectroscopy that DBSA actually participates in the PANI doping process. The PANI doped with DBSA (DBSA-PANI) covering the AC surfaces is observed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical properties of the composites are studied by cyclic voltammetry (CV). The composites show different values of specific capacitance, which was found to be a function of DBSA concentration. The composite prepared in 0.045M DBSA solution shows the highest specific capacitance (115.2Fg−1) among the prepared composites. The doping level of DBSA-PANI is increased with the concentration of DBSA in solution.