The potential ability of paper sludge to remove neutral red (NR) from aqueous solution was investigated using UV-visible and FTIR spectroscophotometers. The stability of the optical properties of NR was assessed in terms of evolution of the main absorption bands of NR in aqueous solution and in NR/incinerated sludge suspension as a function of pH and exposure time. The results showed that, the adsorption kinetic of NR onto incinerated paper sludge was fast as a result of 60.09% removal efficiency obtained within 80 minutes at pH 5. The adsorption reaction was perfectly described by pseudo- second-order kinetic model. The profile of isotherm adsorption of NR onto incinerated sludge was S-shape type. Incinerated sludge exhibited excellent performance for adsorption of NR with a maximum of 374. 98 mg/g. The equilibrium adsorption data were well fitted with Freundlich model. FTIR analysis revealed the strong interaction forces operating on heterogeneous surface of the incinerated sludge between the dissociation of the oxygenated groupings, which are in general acid functional, and dimethylamine goup [-N+(CH3)2 ] of the NR dye which could be used to explain the high adsorption capacity of cationic dye onto incinerated sludge. These findings can support the design of remediation processes and also assist in predict their fate in the environment.