Enhanced removal of dissolved natural organic matter (DOM) by modified granular activated carbons (GACs) was studied. A granular activated carbon (GAC) was modified by high temperature ammonia and steam treatment, respectively. Both techniques increased the carbon mesoporosity and surface basicity. Adsorption isotherms indicated that ammonia-and steam-treated carbons exhibited higher DOM uptake than the precursor mainly due to the enlargement of carbon pores. Rapid small scale column tests (RSSCTs) showed that steam treatment almost doubled the volume of treated water to reach 50% breakthrough compared to the virgin GAC. Several iron impregnation methods were used to load iron species on the carbon surface. Surface-area normalized isotherms showed that some iron impregnated carbons had higher DOM uptake due to the presence of iron species on the carbon surface. However, not all the iron species were favorable for the adsorption. Iron oxidation state and particle size appear to be important. GACs with higher mesoporosity and proper iron dispersion on the surface were expected to exhibit higher DOM uptakes from natural waters.