Biocompatible and biodegradable nanogels with a branched structure designed as potential carriers for drug delivery are reported here. The nanogels were prepared by the reaction of 3,6-dioxaoctan-1,8-diyl bis(ethylene phosphate) (TEGDP) with tris(2-aminoethyl)amine (TREN) in an ionic liquid containing miniemulsion; the particle size was tunable in the nanoscopic range. The biocompatibility of the nanogels was evaluated using both in vitro and in vivo experiments. The nanogels could efficiently load the anticancer drug doxorubicin and showed enzyme-responsive drug release behavior. The nanogels were further labelled with fluorescein isothiocyanate through a reaction with the surface amino groups to demonstrate functionalization. Flow cytometric analyses and confocal laser scanning microscope observations demonstrated that the nanogels could be efficiently taken up by the human breast cancer cell line MDA-MB-231. These biocompatible, biodegradable and surface functionalizable nanogels are expected to have utility in the field of drug delivery.