Anionically charged MWNT with anionic carboxylic acid groups were mixed with cationic organic polymers, such as poly(allyamine hydrochloride) (PAH) and, poly(diallyldimethyl-ammonium chloride) (PDDA) to form polyelectrolyte complexes by coulombic interaction. The complexation behavior of the MWNT was affected by pH when mixed with PAH containing weak basic amine groups. By increasing the content of cationic polymer, the zeta potential of MWNT was increased from a negative values to a positive ones. With higher pH, the isoelectric point of anionic MWNT and cationic PAH increased and the saturated zeta potential value with high PAH content due to the less ionized MWNT and more ionized PAH. On the other hand, strong basic PDDA was less affected by changing pH and showed a similar isoelectric point and saturated zeta potential value with high PAH content. The complexation changed the dispersibility of MWNT in water, with the result that the MWNT was precipitated around the isoelectric point but then re-dispersed with higher cationic polymer content. HR-TEM images confirmed that excess PAH completely covered the MWNT.