Poly(oligoethylene glycol) methyl ether acrylate was polymerized via reversible addition fragmentation transfer polymerization (RAFT), and then chain extended in the presence of both a cross-linker and vinyl benzaldehyde (VBA), yielding monodisperse star polymers. The presence of aldehyde groups in the core was exploited to attach doxorubicin. The drug loading was controlled by the amount of VBA incorporated (until 28 wt in drug). The doxorubicin release was studied at pH = 5.5 and 7.4; conditions representative of endosomal and extra cellular environments. In vitro studies revealed that the doxorubicin-conjugated star polymers had a level of cytotoxicity comparable to that found for free doxorubicin. Confocal microscopy and flow cytometry studies confirmed efficient cell uptake of the star polymers. Well-dispersed biodegradable star polymers are described for conjugating drugs via a pH-responsive linker. Doxorubicin was conjugated to the star cores using amine-aldehyde coupling reactions. Subsequently, the star polymer-doxorubicin conjugates were subjected to in vitro analyses to assess toxicity and doxorubicin release.