Modifying the commercial melamine sponge (MS) that intrinsically possesses highly porous open-cell structure with graphene oxide (GO) or GO-based nanocomposites (NCs) is a facile, effective, and low-cost route to fabricate three-dimensional (3D) porous materials with multifunctionality. Herein, we fabricated two types of 3D MSs that were separately functionalized by the reduced GO (RGO) sheets and Ag/RGO NC through combined methods of chemical reduction and immersion process. The simple immersion process brought out the transition of superhydrophilic MS to highly hydrophobic RGO-MS and Ag/RGO-MS. Due to the unique surface topography and high porosity, the RGO-MS exhibited remarkable absorption capacity of 41-91 times its own weight for a wide range of oils and organic solvents. Both the RGO-MS and Ag/RGO-MS showed excellent oil-water separation efficiencies. The Ag/RGO-MS not only exhibited outstanding absorption capacity and recyclability, but also possessed ideal antibacterial performance towards bacteria of Staphylococcus sciuri, Shewanella MR-1, Pseudoalteromonas lipolytica, and Vibrio natriegens. The Ag/RGO-MS featured with hydrophobicity and antibacterial activity is a promising candidate for potential applications in oil-spill disposal and water disinfection. This study provides an effective strategy for designing and fabricating the 3D porous materials with novel functionalities.