Cellulosic nanomaterials are ideal reinforcers in hydrogel composites, but the current techniques that ensure defined nano-dimensions reduce sustainability. A different strategy for the synthesis of hydrogels from pulp fibers using green chemistry could offer a more sustainable solution. This work explores a mild, straightforward chemical modification with maleic anhydride that simultaneously decorates the fibers with carboxylate and alkene groups. Tuning the temperature of the reaction enables control over the surface charge ranging from 150 to 1,000 μmol/g. The fibers are used to construct a rubber-like, water-stable hydrogel composite prepared by in situ telechelic PEG polymerization followed by thermal or UV-induced free radical crosslinking. The initiation strategy, molecular weight of telechelic PEG, and degree of modification of the fibers enable control over the network formation within and around the fibers. The hydrogel composite is designed to be hydrolytically degradable under alkaline conditions, allowing separate recovery of both fibers and polymer precursors.