This study addresses the removal of crystal violet (CV) from aqueous solutions using solidified landfilled sewage sludge and its modified products as adsorbents. After the sludge was characterized using instrumental techniques (SEM, FTIR, and TG-DTA), adsorption studies were performed in a batch system, and the effects of various experimental parameters were evaluated upon CV adsorption. The results revealed that more irregular pores, higher surface roughness, and a greater content of oxygen functional groups formed in adsorbents derived from direct incineration (SC). Batch experiments revealed that stirring intension had the least effect on CV adsorption. With increasing adsorbent dosage, the CV removal efficiency increased, but the opposite result was observed for the effect of particle size. CV adsorption onto the three adsorbents was a rapid adsorption process and that onto SC was the most rapid, with the first-order kinetic model best describing the adsorption. The equilibrium data fit the Landgmiur isotherm models best, whereas much higher CV adsorption capacity and better adsorption strength onto SC were found. Desorption studies showed that acid solution was beneficial to the desorption process and the desorption rate of acetic acid reached up to about 55%. Those results proved that the solidified landfilled sewage sludge previously modified by incineration treatment was an effective adsorbent for CV removal from aqueous solution.