Activated Carbon-Fe3O4 composites were synthesized using co-precipitation method and used in batch experiments to adsorb Congo red dyes. The effect of adsorbent dosage, temperature and initial dye concentration was investigated. Increase in the adsorbent dosage resulted in the increase of dye adsorption capacity and the optimum dose was found to be 2 g/L. Increase in temperature had slightly negative impact on the adsorption which indicated the exhothermic nature of the adsorption process. Initial dye concentration also had significant impact on the adsorption process as the adsorption capacity of the AC- Fe3O4 adsorbents decreased with increase in dye concentrations. Finally, the obtained adsorption data were fitted to Langmuir adsorption isotherm and the maximum adsorption capacity of Activated Carbon-Fe3O4 adsorbent was found to be around 129.87 mg/g. Overall, the results suggested that synthesized AC- Fe3O4 composites exhibit significant potential to be used as an adsorbent for the removal of organic pollutants from aqueous solutions.