Hybrid nanostructures with unique optical and magnetic properties have attracted considerable interest as effective mediators for medical imaging and therapy. An aqueous-based, self-assembly approach to synthesizing hybrid plasmonic superparamagnetic nanostructures is presented. The building blocks of the hybrid nanostructure include plasmonic gold nanorods (AuNRs) and superparamagnetic iron oxide nanoparticles (SPIONs). The AuNRs were functionalized via carboxyl-bearing surface ligands, and the SPIONs were kept "bare" after synthesis via a surfactant-free thermal decomposition reaction in triethylene glycol. Hybrid SPION-studded AuNR nanostructures were produced upon simple mixing of the components because of the chemisorption of the AuNRs' free carboxyl groups to the SPIONs' surfaces. The reported synthesis strategy is modular in nature and can be expanded to build hybrid nanostructures with a multitude of other plasmonic nanoparticles. With tunable near-infrared absorption peaks and a sufficient number of bound SPIONs, the self-assembled hybrid nanostructures are suitable for biomedical imaging and therapy applications.