Gold nanorods (GNRs) have the potential to be used as imaging and hyperthermia agents for cancer theranostics. Clinical applications of as-synthesized GNRs (i.e., cetyl trimethylammonium bromide (CTAB)-coated GNRs) are currently limited by their cytotoxicity and insufficient colloidal stability. With an aim to address these problems, we developed a self-assembly processing technique for encapsulating GNRs in poly(ethylene oxide)-poly(n-butyl acrylate) (PEO-PnBA) block copolymer (BCP) micelles. This technique uses simple steps of solvent exchange processes, based on the known principles of block copolymer self-assembly. The resultant BCP-encapsulated GNRs were found to be stable against aggregation under physiological salt conditions for indefinite periods of time, which has rarely previously been achieved by other means of encapsulation.