Polymers with advanced architectures can now be readily and reproducibly synthesized using controlled living polymerization. These materials are attractive as potential drug carriers due to their tunable size, versatile methods of drug incorporation and release, and ease of functionalization with targeting ligands. In this work, we report the design and development of macrocyclic brush or “sunflower” polymers, synthesized by controlled radical polymerization of hydrophilic “petals” from a cyclic multimacroinitiator “core”. These nanostructures can be synthesized with low polydispersity and controlled sizes depending on polymerization time. We further demonstrate that folate-functionalized sunflower polymers facilitate receptor-mediated uptake into cancer cells. These materials therefore show potential as drug carriers for anticancer therapies.