The use of Fentons reagent (Fe2+/H2O2) and Fenton-like reagents containing transition metals of Cu(II), Zn(II), Co(II), and Mn(II) for an alum sludge conditioning to improve its dewaterability was investigated in this study. The results obtained were compared with those obtained from conditioning the same alum sludge using cationic and anionic polymers. Experimental results show that Fentons reagent was the best among the Fenton and Fenton-like reagents for the alum sludge conditioning. A considerable effectiveness of capillary suction time (CST) reduction efficiency of 47% can be achieved under test conditions of Fe2+/H2O2 = 20/125 mg/gDS (dry solid) and pH = 6.0. The observation of floc-like particles after Fentons reagent conditioning of alum sludge suggests that the mechanism of Fentons reagent conditioning was different with that of polymer conditioning. In spite of the less efficiency in the CST reduction of Fentons reagent in alum sludge conditioning compared with that of polymer conditioning, is less than that of polymer conditioning.[b1] This study provided an example of proactive treatment engineering, which is aimed at seeking a safe alternative to the use of polymers in sludge conditioning towards achieving a more sustainable sludge management strategy.