This study described the first impedimetric immunosensor reported for the determination of CCR4, a new prostate cancer biomarker. This impedimetric immunosensor was constructed through the modification of disposable indium tin oxide (ITO) sheet with a conjugated pyrrole polymer P(Pyr-Pac) and subsequent immobilization of anti-CC chemokine receptor 4 (CCR4) antibodies. Acid-substituted poly(pyrrole) P(Pyr-Pac) polymer contained a lot of carboxyl groups on its end site, which were suitable for attachment of anti-CCR4 antibodies. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were chosen to investigate electrode preparation stages and, EIS was chosen to detect the CCR4 concentration. Anti-CCR4 antibody attached bio-sensing surface was highly selective to CCR4 antigen, the specific interaction resulted changes in electrochemical signal. Optimization studies containing polymer amount, anti-CCR4 antibody concentration, anti-CCR4 antibody immobilization time and anti-CCR4 antibody-CCR4 antigen interaction time were studied. The developed immunosensor displayed a linear increase with concentrations of CCR4 antigen (0.02-8 pg/mL) and a low detection limit of 6.4 fg/mL. In addition, this biosensor had great reproducibility and repeatability. Moreover, the designed biosensor was successfully used for the quantification of CCR4 antigen in serum samples. The recovery for the spiked serum samples was between 98.25% and 103.99%. The suggested immunosensor illustrated a good selectivity towards some interferents including different biomarkers. This study could establish a new approach for future cancer biomarker detection.