The present study aims to investigate the adsorption of anionic dye, alizarin red s (ARS), on activated clay modified by iron oxide (Fe-clay) in a batch reactor. The adsorption process reached equilibrium within 90 min, and the removal efficiency increased with the enhancement of initial dye concentration, adsorbent dosage, and contact time, but decreased with the enhancement of solution pH. The adsorption kinetics was investigated according to three theoretical models, but the best fit was achieved by the pseudosecond-order kinetics model. The adsorption isotherms could be well-defined with the Langmuir isotherm model instead of the Freundlich isotherm model, and the calculated maximum adsorption capacity was found to be 32.7 mg mg(-1). The obtained results indicate that Fe-clay is suitable for adsorption of ARS from aqueous solutions.