Imidazolium salt-incorporated postcross-linked porous polymers, namely, IL-PVB-pc-80%, were developed, and they were evaluated for the adsorption of rhodamine B (RB) and Cd2+ from aqueous solution. After N-vinylimidazole and p-dichloroxylene were inserted in the skeletons, IL-PVB-pc-80% contained both ionized imidazole moieties and plentiful mesopores. The adsorption experiments indicated that IL-PVB-pc-80% has excellent adsorption properties with a maximum capacity of 693.5 mg/g for RB and 373.3 mg/g for Cd2+. The adsorption mechanism revealed that the incorporated imidazolium salts were significantly beneficial for the adsorption.