The interaction of a cationic dye namely, Methylene blue (MB) with anionic polyelectrolytes, namely, sodium carboxymethyl cellulose (NaCMC) and Sodium heparinate has been investigated by spectrophotometric technique. The polymers induced metachromasy in the dye resulting in the shift of absorption maxima of the dye towards shorter wavelengths. The stability of the complex formed between MB and NaCMC was found to be lesser than that formed between MB and NaHep. This fact was further confirmed by reversal studies using alcohols, urea and electrolytes. The interaction parameters revealed strong binding between MB-Na Hep complexes. The number of binding sites was found to affect metachromatic shift and other interaction parameters. Among the two polyelectrolytes, NaHep has a greater number of binding sites, hence dye aggregation was found to be greater in MB-NaHep complex than in MB-NaCMC complex.