A novel and highly sensitive sensor based on poly[2, 5-di(2-thiophenyl)-1-p-(tolyl) pyrrole] was developed and successfully applied for the electrochemical determination of acetaminophen (AC) in pharmaceutical samples. The voltammetric behaviors of AC on modified pencil graphite electrode were investigated by cyclic voltammetry and differential pulse voltammetry in phosphate buffer solution. The voltammetric studies reveal that the polymer modified pencil graphite electrode possesses a remarkable electrocatalytic activity toward acetaminophen compared with the unmodified pencil graphite electrode. A linear dynamic range from 0.025 to 5 mu M and a correlation coefficient of 0.997 with a slope (sensitivity) of 23 mA M-1 were obtained for AC. The detection limit (S/N = 3) was determined as 1.94 nM, which shows a high sensitivity of the developed sensor for AC.