Abstarct: The performance of glassy carbon electrode (GCE) coated with poly(nicotinic acid) –multiwalled carbon nanotube (MWCNT) composite was investigated in the simultaneous determination of Ascorbic acid (AA), Dopamine (DA) and Uric acid (UA) using voltammetry.The presence of MWCNT and polynicotinic acid improves the sensitivity and reproducibility of the electrode. The effect of several parameters including pH, volume and type of buffer, type of electrolyte, number of cycles polymerization, concentration of nicotinic acid and MWCNTs , scan rate and pulse amplitude on the electrochemical determination of the analytical were studied and optimized. The linear dynamic range of the proposed method were 1.0 – 50.0 µM, 20.0 – 100.0 µM and 1.0 – 40.0 µM for DA, AA and UA, respectively under optimum conditions. Also the detection limits of 0.82 µM, 4.68 µM and 0.49 µM were obtained for DA, AA and UA, respectively. The effects of interfering ions were studied and it was found that sensor has least of interference from most of the common ions due to selective interaction of the modifier functionalities with AA, DA and UA. The response of the electrode remained constant for at least 9 days successive opration. Finally the proposed method was successfully applied for determination of DA, AA and UA in biological samples of blood serum and urine.