Branched polyethylenimine (bPEI) ($M_w=25;k$) conjugated with catechol groups (PEI-C) was crosslinked to produce PEI-catechol nanogels (PCNs), which were used as a new class of small interfering RNA (siRNA) delivery carriers. The conjugated catechol groups were crosslinked with the primary amines of PEI under basic conditions. The size and morphology of the PCNs were analyzed by dynamic light scattering (DLS) and atomic force microscopy (AFM). The resulting PCNs were quite stable and had an average diameter of $111.4{pm}14.8;nm$ in an aqueous solution. Compared to bPEI, the PCNs exhibited much lower cytotoxicity, and formed more stable complexes with siRNA. The PCNs/siRNA complexes exhibited enhanced cellular uptake and promoted gene silencing efficiency, suggesting that they can be used potentially as a less cytotoxic siRNA carrier.