A graft copolymer having drug-containing side chains is described. The graft copolymer can be prepared, for example, by directly polymerizing a drug-containing monomer on multiple sites of a linear copolymer. When exposed to water, the graft copolymer can form uniform nanocarriers, e.g., nanomicelles, optionally encapsulating additional drugs, e.g., non-covalently in the interior of the nanocarriers, for coordinated drug delivery of a plurality of drugs. Also described herein is the use of the nanocarriers for delivery of therapeutic agents, particularly the dual delivery of chemotherapeutic agents to treat tumors.