In this work, hierarchical porous composite hydrogels of poly(acrylic acid)–silver/silver nanoparticles (PAA–Ag/AgNPs) were successfully prepared by an in situ coordination and self-assembly process. The obtained composite PAA–Ag/AgNPs hydrogels were achieved through different coordination times between PAA and silver ions in the self-assembly process. These as-formed hydrogels were characterized by various morphological and spectroscopy techniques. Interestingly, unique 3D porous network structures in the nanocomposite hydrogels were demonstrated, due to which the as-obtained composite hydrogels demonstrate good removal capacities in accordance with both a pseudo-first-order model and a pseudo-second-order model for three model dyes. Thus, the present obtained composite hydrogels provide new alternatives for developing hybrid hydrogels and nanomaterials for removal of organic dye pollutants from aqueous environments in wastewater treatment applications.