Graphene oxide (GO) is an attractive material for water treatment, although its high surface energy restricts its practical application. To overcome this challenge, we have developed a well-dispersed and interconnected, functionalized biopolymeric GO with magnetic activity, namely, cl–CS–p(MA)/Fe 3 O 4 NPs. This three-dimensional, sponge-like nanostructured material is composed of graphene oxide nanosheets dispersed in functionalized chitosan/poly(methacrylic acid) and is cross-linked with in situ-developed Fe 3 O 4 nanoparticles. Methacrylic acid (MA)-functionalized chitosan (CS) cross-linked with N,N-methylenebis(acrylamide) (MBA), designated as cl–CS–p(MA), facilitates the stable dispersion of GO nanosheets, providing a proper solid matrix for the generation of well-dispersed in situ Fe 3 O 4 NPs. The methodology allows for the generation of numerous binding sites with an interconnected morphology, facilitating the rapid uptake of a cationic dye in significant quantity, e.g., methylene blue (MB), which is used as a model water pollutant. In this work, the structural architecture of cl–CS–p(MA)/Fe 3 O 4 NPs was characterized with multiple approaches, and the adsorption mechanism was revealed to be an electrostatic interaction. The synthesized nanocomposite showed significant recyclability and structural stability. Adsorption equilibrium was achieved within 20 min, and the maximum adsorption capacity was 2478 mg/g for MB, surpassing the values reported for any other adsorbents to date.