Adsorption is the adherence to a surface of atoms, ions, or molecules from a gas, liquid, or dissolved solid. This method produces an adsorbent film on the adsorbent's ground. In the present study, Ulva intestinalis (formerly Enteromorpha intestinalis) a member of Cyanophyceae collected form Covelong, Southeast coast of Tamil Nadu was used for adsorbing methyl orange and phenol red. The results showed that at 60 min of treating the phenol red dye with seaweed yield maximum reduction (44%) of colour and in case of methyl orange 47.4% colour reduction occurred after 60 min.