Sustained delivery of therapeutic genes in vitro and in vivo has a wide range of applications in studying biology and in developing therapies for treating disease or repairing tissue. Nonviral vectors such as cationic polymers still present promising approaches; however, bolus transfection methods with polyethylenimine-based DNA polyplexes suffer from considerable levels of cytotoxicity and short-lived transgene expression levels. Here, we designed and characterized a hyaluronic acid-based porous hydrogel system for nonviral gene delivery by loading with surface-associated DNA polyplexes. With this, we observed tunable, enhanced, and sustained transgene expression over 30 days of cell culture with better cell viability and marked improvements over comparable bolus transfection techniques. Finally, we investigated mechanisms thought to be responsible for the sustained expression profile, finding that multiple transfection events are likely responsible for the observed sustained expression.